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Su R, Han C, Chen G, Li H, Liu W, Wang C, Zhang W, Zhang Y, Zhang D, Ma H. Low- and moderate-intensity aerobic exercise improves the physiological acclimatization of lowlanders on the Tibetan plateau. Eur J Sport Sci 2024; 24:834-845. [PMID: 38874991 PMCID: PMC11235882 DOI: 10.1002/ejsc.12110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2023] [Revised: 02/18/2024] [Accepted: 03/28/2024] [Indexed: 06/15/2024]
Abstract
This study investigates whether exercise as a strategy for improving physical fitness at sea level also offers comparable benefits in the unique context of high altitudes (HA), considering the physiological challenges of hypoxic conditions. Overall, 121 lowlanders who had lived on the Tibetan Plateau for >2 years and were still living at HA during the measurements were randomly classified into four groups. Each individual of the low-intensity (LI), moderate-intensity (MI), and high-intensity (HI) groups performed 20 sessions of aerobic exercise at HA (3680 m) over 4 weeks, while the control group (CG) did not undergo any intervention. Physiological responses before and after the intervention were observed. The LI and MI groups experienced significant improvement in cardiopulmonary fitness (0.27 and 0.35 L/min increases in peak oxygen uptake [V ˙ $\dot{\mathrm{V}}$ O2peak], both p < 0.05) after exercise intervention, while the hematocrit (HCT) remained unchanged (p > 0.05). However, HI exercise was less efficient for cardiopulmonary fitness of lowlanders (0.02 L/min decrease inV ˙ $\dot{\mathrm{V}}$ O2peak, p > 0.05), whereas both the HCT (1.74 %, p < 0.001) and glomerular filtration rate (18.41 mL/min, p < 0.001) increased with HI intervention. Therefore, LI and MI aerobic exercise, rather than HI, can help lowlanders in Tibet become more acclimated to the HA by increasing cardiopulmonary function and counteracting erythrocytosis.
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Affiliation(s)
- Rui Su
- Tibet Autonomous Region Key Laboratory of High Altitudes Brain Science and Environmental AcclimationTibet UniversityLhasaChina
- School of Psychological and Cognitive Sciences and Beijing Key Laboratory of Behavior and Mental HealthPeking UniversityBeijingChina
- Academy of Plateau Science and SustainabilityPeople's Government of Qinghai Province/Beijing Normal UniversityBeijingQinghaiChina
| | - Chenxiao Han
- Tibet Autonomous Region Key Laboratory of High Altitudes Brain Science and Environmental AcclimationTibet UniversityLhasaChina
| | - Guiquan Chen
- Department of Acupuncture and RehabilitationThe Affiliated Traditional Chinese Medicine Hospital of Southwest Medical UniversityLuzhouSichuan ProvinceChina
| | - Hao Li
- Tibet Autonomous Region Key Laboratory of High Altitudes Brain Science and Environmental AcclimationTibet UniversityLhasaChina
| | - Wanying Liu
- Tibet Autonomous Region Key Laboratory of High Altitudes Brain Science and Environmental AcclimationTibet UniversityLhasaChina
| | - Chengzhi Wang
- Tibet Autonomous Region Key Laboratory of High Altitudes Brain Science and Environmental AcclimationTibet UniversityLhasaChina
| | - Wenrui Zhang
- Tibet Autonomous Region Key Laboratory of High Altitudes Brain Science and Environmental AcclimationTibet UniversityLhasaChina
| | - Yuming Zhang
- Tibet Autonomous Region Key Laboratory of High Altitudes Brain Science and Environmental AcclimationTibet UniversityLhasaChina
| | - Delong Zhang
- Tibet Autonomous Region Key Laboratory of High Altitudes Brain Science and Environmental AcclimationTibet UniversityLhasaChina
- Key Laboratory of BrainCognition and Education SciencesMinistry of EducationBeijingChina
- School of PsychologyCenter for Studies of Psychological Application, and Guangdong Key Laboratory of Mental Health and Cognitive ScienceSouth China Normal UniversityGuangzhouChina
| | - Hailin Ma
- Tibet Autonomous Region Key Laboratory of High Altitudes Brain Science and Environmental AcclimationTibet UniversityLhasaChina
- Academy of Plateau Science and SustainabilityPeople's Government of Qinghai Province/Beijing Normal UniversityBeijingQinghaiChina
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2
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Webb KL, Gorman EK, Morkeberg OH, Klassen SA, Regimbal RJ, Wiggins CC, Joyner MJ, Hammer SM, Senefeld JW. The relationship between hemoglobin and [Formula: see text]: A systematic review and meta-analysis. PLoS One 2023; 18:e0292835. [PMID: 37824583 PMCID: PMC10569622 DOI: 10.1371/journal.pone.0292835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 09/29/2023] [Indexed: 10/14/2023] Open
Abstract
OBJECTIVE There is widespread agreement about the key role of hemoglobin for oxygen transport. Both observational and interventional studies have examined the relationship between hemoglobin levels and maximal oxygen uptake ([Formula: see text]) in humans. However, there exists considerable variability in the scientific literature regarding the potential relationship between hemoglobin and [Formula: see text]. Thus, we aimed to provide a comprehensive analysis of the diverse literature and examine the relationship between hemoglobin levels (hemoglobin concentration and mass) and [Formula: see text] (absolute and relative [Formula: see text]) among both observational and interventional studies. METHODS A systematic search was performed on December 6th, 2021. The study procedures and reporting of findings followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Article selection and data abstraction were performed in duplicate by two independent reviewers. Primary outcomes were hemoglobin levels and [Formula: see text] values (absolute and relative). For observational studies, meta-regression models were performed to examine the relationship between hemoglobin levels and [Formula: see text] values. For interventional studies, meta-analysis models were performed to determine the change in [Formula: see text] values (standard paired difference) associated with interventions designed to modify hemoglobin levels or [Formula: see text]. Meta-regression models were then performed to determine the relationship between a change in hemoglobin levels and the change in [Formula: see text] values. RESULTS Data from 384 studies (226 observational studies and 158 interventional studies) were examined. For observational data, there was a positive association between absolute [Formula: see text] and hemoglobin levels (hemoglobin concentration, hemoglobin mass, and hematocrit (P<0.001 for all)). Prespecified subgroup analyses demonstrated no apparent sex-related differences among these relationships. For interventional data, there was a positive association between the change of absolute [Formula: see text] (standard paired difference) and the change in hemoglobin levels (hemoglobin concentration (P<0.0001) and hemoglobin mass (P = 0.006)). CONCLUSION These findings suggest that [Formula: see text] values are closely associated with hemoglobin levels among both observational and interventional studies. Although our findings suggest a lack of sex differences in these relationships, there were limited studies incorporating females or stratifying results by biological sex.
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Affiliation(s)
- Kevin L. Webb
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Ellen K. Gorman
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Olaf H. Morkeberg
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Stephen A. Klassen
- Department of Kinesiology, Brock University, St. Catharines, Ontario, Canada
| | - Riley J. Regimbal
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Chad C. Wiggins
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Michael J. Joyner
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Shane M. Hammer
- Department of Kinesiology, Applied Health, and Recreation, Oklahoma State University, Stillwater, Oklahoma, United States of America
| | - Jonathon W. Senefeld
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, Minnesota, United States of America
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, United States of America
- Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, Illinois
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3
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Niclou A, Sarma M, Levy S, Ocobock C. To the extreme! How biological anthropology can inform exercise physiology in extreme environments. Comp Biochem Physiol A Mol Integr Physiol 2023; 284:111476. [PMID: 37423419 DOI: 10.1016/j.cbpa.2023.111476] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Revised: 07/03/2023] [Accepted: 07/04/2023] [Indexed: 07/11/2023]
Abstract
The fields of biological anthropology and exercise physiology are closely related and can provide mutually beneficial insights into human performance. These fields often use similar methods and are both interested in how humans function, perform, and respond in extreme environments. However, these two fields have different perspectives, ask different questions, and work within different theoretical frameworks and timescales. Biological anthropologists and exercise physiologists can greatly benefit from working together when examining human adaptation, acclimatization, and athletic performance in the extremes of heat, cold, and high-altitude. Here we review the adaptations and acclimatizations in these three different extreme environments. We then examine how this work has informed and built upon exercise physiology research on human performance. Finally, we present an agenda for moving forward, hopefully, with these two fields working more closely together to produce innovative research that improves our holistic understanding of human performance capacities informed by evolutionary theory, modern human acclimatization, and the desire to produce immediate and direct benefits.
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Affiliation(s)
- Alexandra Niclou
- Pennington Biomedical Research Center, Baton Rouge, LA, United States of America. https://twitter.com/fiat_luxandra
| | - Mallika Sarma
- Human Space Flight Lab, Johns Hopkins School of Medicine, Baltimore, MD, United States of America. https://twitter.com/skyy_mal
| | - Stephanie Levy
- Department of Anthropology, CUNY Hunter College, New York, NY, United States of America; New York Consortium in Evolutionary Primatology, New York, NY, United States of America. https://twitter.com/slevyscience
| | - Cara Ocobock
- University of Notre Dame Department of Anthropology, Notre Dame, IN, United States of America; Eck Institute for Global Health, Institute for Educational Initiatives, University of Notre Dame, United States of America.
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Abstract
With ascent to high altitude, barometric pressure declines, leading to a reduction in the partial pressure of oxygen at every point along the oxygen transport chain from the ambient air to tissue mitochondria. This leads, in turn, to a series of changes over varying time frames across multiple organ systems that serve to maintain tissue oxygen delivery at levels sufficient to prevent acute altitude illness and preserve cognitive and locomotor function. This review focuses primarily on the physiological adjustments and acclimatization processes that occur in the lungs of healthy individuals, including alterations in control of breathing, ventilation, gas exchange, lung mechanics and dynamics, and pulmonary vascular physiology. Because other organ systems, including the cardiovascular, hematologic and renal systems, contribute to acclimatization, the responses seen in these systems, as well as changes in common activities such as sleep and exercise, are also addressed. While the pattern of the responses highlighted in this review are similar across individuals, the magnitude of such responses often demonstrates significant interindividual variability which accounts for subsequent differences in tolerance of the low oxygen conditions in this environment.
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Affiliation(s)
- Marc Moritz Berger
- Department of Anesthesiology and Intensive Care Medicine, University Hospital Essen, University Duisburg-Essen, Essen, Germany
| | - Andrew M Luks
- Division of Pulmonary, Critical Care and Sleep Medicine, University of Washington, Seattle, Washington
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Bourdillon N, Subudhi AW, Fan JL, Evero O, Elliott JE, Lovering AT, Roach RC, Kayser B. AltitudeOmics: effects of 16 days acclimatization to hypobaric hypoxia on muscle oxygen extraction during incremental exercise. J Appl Physiol (1985) 2023; 135:823-832. [PMID: 37589059 PMCID: PMC10642515 DOI: 10.1152/japplphysiol.00100.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 07/11/2023] [Accepted: 08/03/2023] [Indexed: 08/18/2023] Open
Abstract
Acute altitude exposure lowers arterial oxygen content ([Formula: see text]) and cardiac output ([Formula: see text]) at peak exercise, whereas O2 extraction from blood to working muscles remains similar. Acclimatization normalizes [Formula: see text] but not peak [Formula: see text] nor peak oxygen consumption (V̇o2peak). To what extent acclimatization impacts muscle O2 extraction remains unresolved. Twenty-one sea-level residents performed an incremental cycling exercise to exhaustion near sea level (SL), in acute (ALT1) and chronic (ALT16) hypoxia (5,260 m). Arterial blood gases, gas exchange at the mouth and oxy- (O2Hb) and deoxyhemoglobin (HHb) of the vastus lateralis were recorded to assess arterial O2 content ([Formula: see text]), [Formula: see text], and V̇o2. The HHb-V̇o2 slope was taken as a surrogate for muscle O2 extraction. During moderate-intensity exercise, HHb-V̇o2 slope increased to a comparable extent at ALT1 (2.13 ± 0.94) and ALT16 (2.03 ± 0.88) compared with SL (1.27 ± 0.12), indicating increased O2 extraction. However, the HHb/[Formula: see text] ratio increased from SL to ALT1 and then tended to go back to SL values at ALT16. During high-intensity exercise, HHb-V̇o2 slope reached a break point beyond which it decreased at SL and ALT1, but not at ALT16. Increased muscle O2 extraction during submaximal exercise was associated with decreased [Formula: see text] in acute hypoxia. The significantly greater muscle O2 extraction during maximal exercise in chronic hypoxia is suggestive of an O2 reserve.NEW & NOTEWORTHY During incremental exercise muscle deoxyhemoglobin (HHb) and oxygen consumption (V̇o2) both increase linearly, and the slope of their relationship is an indirect index of local muscle O2 extraction. The latter was assessed at sea level, in acute and during chronic exposure to 5,260 m. The demonstrated presence of a muscle O2 extraction reserve during chronic exposure is coherent with previous studies indicating both limited muscle oxidative capacity and decrease in motor drive.
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Affiliation(s)
- Nicolas Bourdillon
- Institute of Sports Sciences, University of Lausanne, Lausanne, Switzerland
| | - Andrew W Subudhi
- Hybl Sports Medicine and Performance Center, Department of Human Physiology and Nutrition, University of Colorado, Colorado Springs, Colorado, United States
| | - Jui-Lin Fan
- Department of Physiology, Faculty of Medical & Health Sciences, Manaaki Manawa-The Centre for Heart Research, University of Auckland, Auckland, New Zealand
| | - Oghenero Evero
- Altitude Research Center, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States
| | - Jonathan E Elliott
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States
| | - Robert C Roach
- Altitude Research Center, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States
| | - Bengt Kayser
- Institute of Sports Sciences, University of Lausanne, Lausanne, Switzerland
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Cherouveim ED, Miliotis PG, Koskolou MD, Dipla K, Vrabas IS, Geladas ND. The Effect of Skeletal Muscle Oxygenation on Hemodynamics, Cerebral Oxygenation and Activation, and Exercise Performance during Incremental Exercise to Exhaustion in Male Cyclists. BIOLOGY 2023; 12:981. [PMID: 37508410 PMCID: PMC10376807 DOI: 10.3390/biology12070981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2023] [Revised: 06/28/2023] [Accepted: 07/06/2023] [Indexed: 07/30/2023]
Abstract
This study aimed to elucidate whether muscle blood flow restriction during maximal exercise is associated with alterations in hemodynamics, cerebral oxygenation, cerebral activation, and deterioration of exercise performance in male participants. Thirteen healthy males, cyclists (age 33 ± 2 yrs., body mass: 78.6 ± 2.5 kg, and body mass index: 25.57 ± 0.91 kg·m-1), performed a maximal incremental exercise test on a bicycle ergometer in two experimental conditions: (a) with muscle blood flow restriction through the application of thigh cuffs inflated at 120 mmHg (with cuffs, WC) and (b) without restriction (no cuffs, NC). Exercise performance significantly deteriorated with muscle blood flow restriction, as evidenced by the reductions in V˙O2max (-17 ± 2%, p < 0.001), peak power output (-28 ± 2%, p < 0.001), and time to exhaustion (-28 ± 2%, p < 0.001). Muscle oxygenated hemoglobin (Δ[O2Hb]) during exercise declined more in the NC condition (p < 0.01); however, at exhaustion, the magnitude of muscle oxygenation and muscle deoxygenation were similar between conditions (p > 0.05). At maximal effort, lower cerebral deoxygenated hemoglobin (Δ[HHb]) and cerebral total hemoglobin (Δ[THb]) were observed in WC (p < 0.001), accompanied by a lower cardiac output, heart rate, and stroke volume vs. the NC condition (p < 0.01), whereas systolic blood pressure, rating of perceived exertion, and cerebral activation (as assessed by electroencephalography (EEG) activity) were similar (p > 0.05) between conditions at task failure, despite marked differences in exercise duration, maximal aerobic power output, and V˙O2max. In conclusion, in trained cyclists, muscle blood flow restriction during an incremental cycling exercise test significantly limited exercise performance. Exercise intolerance with muscle blood flow restriction was mainly associated with attenuated cardiac responses, despite cerebral activation reaching similar maximal levels as without muscle blood flow restriction.
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Affiliation(s)
- Evgenia D Cherouveim
- Division of Sports Medicine and Biology of Exercise, School of Physical Education and Sports Science, National and Kapodistrian University of Athens, 17237 Athens, Greece
| | - Panagiotis G Miliotis
- Division of Sports Medicine and Biology of Exercise, School of Physical Education and Sports Science, National and Kapodistrian University of Athens, 17237 Athens, Greece
| | - Maria D Koskolou
- Division of Sports Medicine and Biology of Exercise, School of Physical Education and Sports Science, National and Kapodistrian University of Athens, 17237 Athens, Greece
| | - Konstantina Dipla
- Laboratory of Exercise Physiology and Biochemistry, School of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, 62122 Serres, Greece
| | - Ioannis S Vrabas
- Laboratory of Exercise Physiology and Biochemistry, School of Physical Education and Sports Science at Serres, Aristotle University of Thessaloniki, 62122 Serres, Greece
| | - Nickos D Geladas
- Division of Sports Medicine and Biology of Exercise, School of Physical Education and Sports Science, National and Kapodistrian University of Athens, 17237 Athens, Greece
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Zubieta-Calleja GR, Zubieta-DeUrioste N. High Altitude Pulmonary Edema, High Altitude Cerebral Edema, and Acute Mountain Sickness: an enhanced opinion from the High Andes - La Paz, Bolivia 3,500 m. REVIEWS ON ENVIRONMENTAL HEALTH 2023; 38:327-338. [PMID: 35487499 DOI: 10.1515/reveh-2021-0172] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 03/21/2022] [Indexed: 06/02/2023]
Abstract
Traveling to high altitudes for entertainment or work is sometimes associated with acute high altitude pathologies. In the past, scientific literature from the lowlander point of view was primarily based on mountain climbing. Sea level scientists developed all guidelines, but they need modifications for medical care in high altitude cities. Acute Mountain Sickness, High Altitude Pulmonary Edema, and High Altitude Cerebral Edema are medical conditions that some travelers can face. We present how to diagnose and treat acute high altitude pathologies, based on 51 years of high altitude physiology research and medical practice in hypobaric hypoxic diseases in La Paz, Bolivia (3,600 m; 11,811 ft), at the High Altitude Pulmonary and Pathology Institute (HAPPI - IPPA). These can occasionally present after flights to high altitude cities, both in lowlanders or high-altitude residents during re-entry. Acute high altitude ascent diseases can be adequately diagnosed and treated in high altitude cities following the presented guidelines. Treating these high-altitude illnesses, we had no loss of life. Traveling to a high altitude with sound medical advice should not be feared as it has many benefits. Nowadays, altitude descent and evacuation are not mandatory in populated highland cities, with adequate medical resources.
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Affiliation(s)
- Gustavo R Zubieta-Calleja
- High Altitude Pulmonary and Pathology Institute (HAPPI-IPPA), La Paz, Bolivia
- Department of Physiology, Shri B.M. Patil Medical College, Hospital and Research Centre, BLDE (Deemed to be University), Vijayapur 586103, Karnataka, India
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Simpson LL, Hansen AB, Moralez G, Amin SB, Hofstaetter F, Gasho C, Stembridge M, Dawkins TG, Tymko MM, Ainslie PN, Lawley JS, Hearon CM. Adrenergic control of skeletal muscle blood flow during chronic hypoxia in healthy males. Am J Physiol Regul Integr Comp Physiol 2023; 324:R457-R469. [PMID: 36717165 PMCID: PMC10026988 DOI: 10.1152/ajpregu.00230.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 01/24/2023] [Accepted: 01/24/2023] [Indexed: 02/01/2023]
Abstract
Sympathetic transduction is reduced following chronic high-altitude (HA) exposure; however, vascular α-adrenergic signaling, the primary mechanism mediating sympathetic vasoconstriction at sea level (SL), has not been examined at HA. In nine male lowlanders, we measured forearm blood flow (Doppler ultrasound) and calculated changes in vascular conductance (ΔFVC) during 1) incremental intra-arterial infusion of phenylephrine to assess α1-adrenergic receptor responsiveness and 2) combined intra-arterial infusion of β-adrenergic and α-adrenergic antagonists propranolol and phentolamine (α-β-blockade) to assess adrenergic vascular restraint at rest and during exercise-induced sympathoexcitation (cycling; 60% peak power). Experiments were performed near SL (344 m) and after 3 wk at HA (4,383 m). HA abolished the vasoconstrictor response to low-dose phenylephrine (ΔFVC: SL: -34 ± 15%, vs. HA; +3 ± 18%; P < 0.0001) and markedly attenuated the response to medium (ΔFVC: SL: -45 ± 18% vs. HA: -28 ± 11%; P = 0.009) and high (ΔFVC: SL: -47 ± 20%, vs. HA: -35 ± 20%; P = 0.041) doses. Blockade of β-adrenergic receptors alone had no effect on resting FVC (P = 0.500) and combined α-β-blockade induced a similar vasodilatory response at SL and HA (P = 0.580). Forearm vasoconstriction during cycling was not different at SL and HA (P = 0.999). Interestingly, cycling-induced forearm vasoconstriction was attenuated by α-β-blockade at SL (ΔFVC: Control: -27 ± 128 vs. α-β-blockade: +19 ± 23%; P = 0.0004), but unaffected at HA (ΔFVC: Control: -20 ± 22 vs. α-β-blockade: -23 ± 11%; P = 0.999). Our results indicate that in healthy males, altitude acclimatization attenuates α1-adrenergic receptor responsiveness; however, resting α-adrenergic restraint remains intact, due to concurrent resting sympathoexcitation. Furthermore, forearm vasoconstrictor responses to cycling are preserved, although the contribution of adrenergic receptors is diminished, indicating a reliance on alternative vasoconstrictor mechanisms.
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Affiliation(s)
- Lydia L Simpson
- Department of Sport Science, Division of Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
| | - Alexander B Hansen
- Department of Sport Science, Division of Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
| | - Gilbert Moralez
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas, United States
| | - Sachin B Amin
- Department of Sport Science, Division of Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
| | - Florian Hofstaetter
- Department of Sport Science, Division of Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
| | - Christopher Gasho
- Department of Medicine, Division of Pulmonary and Critical Care, Loma Linda University, Loma Linda, California, United States
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, Wales, United Kingdom
| | - Tony G Dawkins
- Centre of Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Michael M Tymko
- Centre of Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
- Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
- Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Philip N Ainslie
- Centre of Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Justin S Lawley
- Department of Sport Science, Division of Performance Physiology and Prevention, Universität Innsbruck, Innsbruck, Austria
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Christopher M Hearon
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas, United States
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas, United States
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Seiler T, Nakas CT, Brill AK, Hefti U, Hilty MP, Perret-Hoigné E, Sailer J, Kabitz HJ, Merz TM, Pichler Hefti J. Do cardiopulmonary exercise tests predict summit success and acute mountain sickness? A prospective observational field study at extreme altitude. Br J Sports Med 2023:bjsports-2022-106211. [PMID: 36898769 DOI: 10.1136/bjsports-2022-106211] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/22/2023] [Indexed: 03/12/2023]
Abstract
OBJECTIVE During a high-altitude expedition, the association of cardiopulmonary exercise testing (CPET) parameters with the risk of developing acute mountain sickness (AMS) and the chance of reaching the summit were investigated. METHODS Thirty-nine subjects underwent maximal CPET at lowlands and during ascent to Mount Himlung Himal (7126 m) at 4844 m, before and after 12 days of acclimatisation, and at 6022 m. Daily records of Lake-Louise-Score (LLS) determined AMS. Participants were categorised as AMS+ if moderate to severe AMS occurred. RESULTS Maximal oxygen uptake (V̇O2max) decreased by 40.5%±13.7% at 6022 m and improved after acclimatisation (all p<0.001). Ventilation at maximal exercise (VEmax) was reduced at 6022 m, but higher VEmax was related to summit success (p=0.031). In the 23 AMS+ subjects (mean LLS 7.4±2.4), a pronounced exercise-induced oxygen desaturation (ΔSpO2exercise) was found after arrival at 4844 m (p=0.005). ΔSpO2exercise >-14.0% identified 74% of participants correctly with a sensitivity of 70% and specificity of 81% for predicting moderate to severe AMS. All 15 summiteers showed higher V̇O2max (p<0.001), and a higher risk of AMS in non-summiteers was suggested but did not reach statistical significance (OR: 3.64 (95% CI: 0.78 to 17.58), p=0.057). V̇O2max ≥49.0 mL/min/kg at lowlands and ≥35.0 mL/min/kg at 4844 m predicted summit success with a sensitivity of 46.7% and 53.3%, and specificity of 83.3% and 91.3%, respectively. CONCLUSION Summiteers were able to sustain higher VEmax throughout the expedition. Baseline V̇O2max below 49.0 mL/min/kg was associated with a high chance of 83.3% for summit failure, when climbing without supplemental oxygen. A pronounced drop of SpO2exercise at 4844 m may identify climbers at higher risk of AMS.
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Affiliation(s)
- Thomas Seiler
- Department of Pulmonary Medicine, Inselspital,Bern University Hospital, University of Bern, Bern, Switzerland
| | - Christos T Nakas
- Institute of Clinical Chemistry, Inselspital University Hospital, University of Bern, Bern, Switzerland.,Laboratory of Biometry, University of Thessaly, Volos, Greece
| | - Anne-Kathrin Brill
- Department of Pulmonary Medicine, Inselspital,Bern University Hospital, University of Bern, Bern, Switzerland
| | - Urs Hefti
- Swiss Sportclinic, Bern, Switzerland
| | - Matthias Peter Hilty
- Department of Intensive Care Medicine, University Hospital Zurich, Zurich, Switzerland
| | - Eveline Perret-Hoigné
- Department of Pediatrics, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Jannis Sailer
- Swiss Sportclinic, Bern, Switzerland.,Orthopedics and Traumatology, Hospital Nidwalden, Stans, Switzerland
| | - Hans-Joachim Kabitz
- Department of Internal Medicine II Pneumology Cardiology Intensive Care Medicine, Klinikum Konstanz, Konstanz, Germany
| | - Tobias M Merz
- Cardiovascular Intensive Care Unit, Auckland City Hospital, Auckland, New Zealand.,Department of Intensive Care Medicine, Inselspital, Bern University Hospital, University of Bern, University of Bern, Bern, Switzerland
| | - Jacqueline Pichler Hefti
- Department of Pulmonary Medicine, Inselspital,Bern University Hospital, University of Bern, Bern, Switzerland .,Swiss Sportclinic, Bern, Switzerland
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10
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Gao C, Yang B, Li Y, Pei W. A monocarboxylate transporter-dependent mechanism confers resistance to exercise-induced fatigue in a high-altitude hypoxic environment. Sci Rep 2023; 13:2949. [PMID: 36807596 PMCID: PMC9941081 DOI: 10.1038/s41598-023-30093-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2022] [Accepted: 02/15/2023] [Indexed: 02/22/2023] Open
Abstract
The body is more prone to fatigue in a high-altitude hypoxic environment, in which fatigue occurs in both peripheral muscles and the central nervous system (CNS). The key factor determining the latter is the imbalance in brain energy metabolism. During strenuous exercise, lactate released from astrocytes is taken up by neurons via monocarboxylate transporters (MCTs) as a substrate for energy metabolism. The present study investigated the correlations among the adaptability to exercise-induced fatigue, brain lactate metabolism and neuronal hypoxia injury in a high-altitude hypoxic environment. Rats were subjected to exhaustive incremental load treadmill exercise under either normal pressure and normoxic conditions or simulated high-altitude, low-pressure and hypoxic conditions, with subsequent evaluation of the average exhaustive time as well as the expression of MCT2 and MCT4 in the cerebral motor cortex, the average neuronal density in the hippocampus, and the brain lactate content. The results illustrate that the average exhaustive time, neuronal density, MCT expression and brain lactate content were positively correlated with the altitude acclimatization time. These findings demonstrate that an MCT-dependent mechanism is involved in the adaptability of the body to central fatigue and provide a potential basis for medical intervention for exercise-induced fatigue in a high-altitude hypoxic environment.
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Affiliation(s)
- Chen Gao
- Department of General Practice, The 940Th Hospital of Joint Logistics Support Force of Chinese People's Liberation Army, BinHe South Road, No.333, Lanzhou, 730050, Gansu, China.
| | - Binni Yang
- Department of General Practice, The 940Th Hospital of Joint Logistics Support Force of Chinese People’s Liberation Army, BinHe South Road, No.333, Lanzhou, 730050 Gansu China
| | - Yurong Li
- Department of General Practice, The 940Th Hospital of Joint Logistics Support Force of Chinese People’s Liberation Army, BinHe South Road, No.333, Lanzhou, 730050 Gansu China
| | - Wenjuan Pei
- Department of General Practice, The 940Th Hospital of Joint Logistics Support Force of Chinese People’s Liberation Army, BinHe South Road, No.333, Lanzhou, 730050 Gansu China
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11
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Stöhr EJ. The healthy heart does not control a specific cardiac output: a plea for a new interpretation of normal cardiac function. Am J Physiol Heart Circ Physiol 2022; 323:H1239-H1243. [PMID: 36269649 DOI: 10.1152/ajpheart.00535.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The current evidence suggests that the healthy heart does not sense the optimal cardiac output (Q̇) because the different organ systems that influence cardiac function do not interact to adjust their individual responses toward a specific Q̇. Consequently, it is conceivable that the complex cycle of cardiac contraction and relaxation must occur for reasons other than to produce a specific target Q̇ and that there is likely a yet undiscovered overarching principle in the cardiovascular system that explains the combined effects of the prevailing preload, afterload, and contractility. Future research should embrace the possibility of a different purpose to cardiac function than previously assumed and examine the biological capacity of this fascinating organ accordingly.
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Affiliation(s)
- Eric J Stöhr
- COR-HELIX (CardiOvascular Regulation and Human Exercise Laboratory - Integration and Xploration), Leibniz University Hannover, Hannover, Germany
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12
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Furian M, Tannheimer M, Burtscher M. Effects of Acute Exposure and Acclimatization to High-Altitude on Oxygen Saturation and Related Cardiorespiratory Fitness in Health and Disease. J Clin Med 2022; 11:6699. [PMID: 36431176 PMCID: PMC9697047 DOI: 10.3390/jcm11226699] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 11/08/2022] [Accepted: 11/09/2022] [Indexed: 11/16/2022] Open
Abstract
Maximal values of aerobic power (VO2max) and peripheral oxygen saturation (SpO2max) decline in parallel with gain in altitude. Whereas this relationship has been well investigated when acutely exposed to high altitude, potential benefits of acclimatization on SpO2 and related VO2max in healthy and diseased individuals have been much less considered. Therefore, this narrative review was primarily aimed to identify relevant literature reporting altitude-dependent changes in determinants, in particular SpO2, of VO2max and effects of acclimatization in athletes, healthy non-athletes, and patients suffering from cardiovascular, respiratory and/or metabolic diseases. Moreover, focus was set on potential differences with regard to baseline exercise performance, age and sex. Main findings of this review emphasize the close association between individual SpO2 and VO2max, and demonstrate similar altitude effects (acute and during acclimatization) in healthy people and those suffering from cardiovascular and metabolic diseases. However, in patients with ventilatory constrains, i.e., chronic obstructive pulmonary disease, steep decline in SpO2 and V̇O2max and reduced potential to acclimatize stress the already low exercise performance. Finally, implications for prevention and therapy are briefly discussed.
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Affiliation(s)
- Michael Furian
- Pulmonary Division, University Hospital Zurich, 8092 Zurich, Switzerland
- Research Department, Swiss University of Traditional Chinese Medicine, 5330 Bad Zurzach, Switzerland
| | - Markus Tannheimer
- Department of Sport and Rehabilitation Medicine, University of Ulm, 89075 Ulm, Germany
| | - Martin Burtscher
- Department of Sport Science, University of Innsbruck, 6020 Innsbruck, Austria
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13
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Zhong Z, Dong H, Wu Y, Zhou S, Li H, Huang P, Tian H, Li X, Xiao H, Yang T, Xiong K, Zhang G, Tang Z, Li Y, Fan X, Yuan C, Ning J, Li Y, Xie J, Li P. Remote ischemic preconditioning enhances aerobic performance by accelerating regional oxygenation and improving cardiac function during acute hypobaric hypoxia exposure. Front Physiol 2022; 13:950086. [PMID: 36160840 PMCID: PMC9500473 DOI: 10.3389/fphys.2022.950086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2022] [Accepted: 08/08/2022] [Indexed: 12/02/2022] Open
Abstract
Remote ischemic preconditioning (RIPC) may improve exercise performance. However, the influence of RIPC on aerobic performance and underlying physiological mechanisms during hypobaric hypoxia (HH) exposure remains relatively uncertain. Here, we systematically evaluated the potential performance benefits and underlying mechanisms of RIPC during HH exposure. Seventy-nine healthy participants were randomly assigned to receive sham intervention or RIPC (4 × 5 min occlusion 180 mm Hg/reperfusion 0 mm Hg, bilaterally on the upper arms) for 8 consecutive days in phases 1 (24 participants) and phase 2 (55 participants). In the phases 1, we measured the change in maximal oxygen uptake capacity (VO2max) and muscle oxygenation (SmO2) on the leg during a graded exercise test. We also measured regional cerebral oxygenation (rSO2) on the forehead. These measures and physiological variables, such as cardiovascular hemodynamic parameters and heart rate variability index, were used to evaluate the intervention effect of RIPC on the changes in bodily functions caused by HH exposure. In the phase 2, plasma protein mass spectrometry was then performed after RIPC intervention, and the results were further evaluated using ELISA tests to assess possible mechanisms. The results suggested that RIPC intervention improved VO2max (11.29%) and accelerated both the maximum (18.13%) and minimum (53%) values of SmO2 and rSO2 (6.88%) compared to sham intervention in hypobaric hypoxia exposure. Cardiovascular hemodynamic parameters (SV, SVRI, PPV% and SpMet%) and the heart rate variability index (Mean RR, Mean HR, RMSSD, pNN50, Lfnu, Hfnu, SD1, SD2/SD1, ApEn, SampEn, DFA1and DFA2) were evaluated. Protein sequence analysis showed 42 unregulated and six downregulated proteins in the plasma of the RIPC group compared to the sham group after HH exposure. Three proteins, thymosin β4 (Tβ4), heat shock protein-70 (HSP70), and heat shock protein-90 (HSP90), were significantly altered in the plasma of the RIPC group before and after HH exposure. Our data demonstrated that in acute HH exposure, RIPC mitigates the decline in VO2max and regional oxygenation, as well as physiological variables, such as cardiovascular hemodynamic parameters and the heart rate variability index, by influencing plasma Tβ4, HSP70, and HSP90. These data suggest that RIPC may be beneficial for acute HH exposure.
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Affiliation(s)
- Zhifeng Zhong
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Huaping Dong
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Yu Wu
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Simin Zhou
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Hong Li
- Department of Anesthesiology, Xinqiao Hospital, Army Medical University (Third Military Medical University), Chongqing, China
| | - Pei Huang
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Huaijun Tian
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Xiaoxu Li
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
| | - Heng Xiao
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Tian Yang
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
| | - Kun Xiong
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
| | - Gang Zhang
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education of China, Army Medical University (Third Military Medical University), Chongqing, China
| | - Zhongwei Tang
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
| | - Yaling Li
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Xueying Fan
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
| | - Chao Yuan
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education of China, Army Medical University (Third Military Medical University), Chongqing, China
| | - Jiaolin Ning
- Department of Anesthesiology, First Affiliated Hospital, Army Medical University (Third Military Medical University), Chongqing, China
| | - Yue Li
- Department of Anesthesiology, First Affiliated Hospital, Army Medical University (Third Military Medical University), Chongqing, China
| | - Jiaxin Xie
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
- *Correspondence: Jiaxin Xie, ; Peng Li,
| | - Peng Li
- Department of High Altitude Operational Medicine, College of High Altitude Military Medicine, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of High Altitude Medicine, PLA, Army Medical University (Third Military Medical University), Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education of China, Army Medical University (Third Military Medical University), Chongqing, China
- *Correspondence: Jiaxin Xie, ; Peng Li,
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14
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Hansen AB, Moralez G, Amin SB, Hofstätter F, Simpson LL, Gasho C, Tymko MM, Ainslie PN, Lawley JS, Hearon CM. Global REACH 2018: increased adrenergic restraint of blood flow preserves coupling of oxygen delivery and demand during exercise at high-altitude. J Physiol 2022; 600:3483-3495. [PMID: 35738560 PMCID: PMC9357095 DOI: 10.1113/jp282972] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Accepted: 06/16/2022] [Indexed: 01/05/2023] Open
Abstract
Chronic exposure to hypoxia (high-altitude, HA; >4000 m) attenuates the vasodilatory response to exercise and is associated with a persistent increase in basal sympathetic nerve activity (SNA). The mechanism(s) responsible for the reduced vasodilatation and exercise hyperaemia at HA remains unknown. We hypothesized that heightened adrenergic signalling restrains skeletal muscle blood flow during handgrip exercise in lowlanders acclimatizing to HA. We tested nine adult males (n = 9) at sea-level (SL; 344 m) and following 21-28 days at HA (∼4300 m). Forearm blood flow (FBF; duplex ultrasonography), mean arterial pressure (MAP; brachial artery catheter), forearm vascular conductance (FVC; FBF/MAP), and arterial and venous blood sampling (O2 delivery ( DO2${D}_{{{\rm{O}}}_{\rm{2}}}$ ) and uptake ( V̇O2${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ )) were measured at rest and during graded rhythmic handgrip exercise (5%, 15% and 25% of maximum voluntary isometric contraction; MVC) before and after local α- and β-adrenergic blockade (intra-arterial phentolamine and propranolol). HA reduced ΔFBF (25% MVC: SL: 138.3 ± 47.6 vs. HA: 113.4 ± 37.1 ml min-1 ; P = 0.022) and Δ V̇O2${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ (25% MVC: SL: 20.3 ± 7.5 vs. HA: 14.3 ± 6.2 ml min-1 ; P = 0.014) during exercise. Local adrenoreceptor blockade at HA restored FBF during exercise (25% MVC: SLα-β blockade : 164.1 ± 71.7 vs. HAα-β blockade : 185.4 ± 66.6 ml min-1 ; P = 0.947) but resulted in an exaggerated relationship between DO2${D}_{{{\rm{O}}}_{\rm{2}}}$ and V̇O2${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ ( DO2${D}_{{{\rm{O}}}_{\rm{2}}}$ / V̇O2${\dot{V}}_{{{\rm{O}}}_{\rm{2}}}$ slope: SL: 1.32; HA: slope: 1.86; P = 0.037). These results indicate that tonic adrenergic signalling restrains exercise hyperaemia in lowlanders acclimatizing to HA. The increase in adrenergic restraint is necessary to match oxygen delivery to demand and prevent over perfusion of contracting muscle at HA. KEY POINTS: In exercising skeletal muscle, local vasodilatory signalling and sympathetic vasoconstriction integrate to match oxygen delivery to demand and maintain arterial blood pressure. Exposure to chronic hypoxia (altitude, >4000 m) causes a persistent increase in sympathetic nervous system activity that is associated with impaired functional capacity and diminished vasodilatation during exercise. In healthy male lowlanders exposed to chronic hypoxia (21-28 days; ∼4300 m), local adrenoreceptor blockade (combined α- and β-adrenergic blockade) restored skeletal muscle blood flow during handgrip exercise. However, removal of tonic adrenergic restraint at high altitude caused an excessive rise in blood flow and subsequently oxygen delivery for any given metabolic demand. This investigation is the first to identify greater adrenergic restraint of blood flow during acclimatization to high altitude and provides evidence of a functional role for this adaptive response in regulating oxygen delivery and demand.
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Affiliation(s)
| | - Gilbert Moralez
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, TX, USA
| | - Sachin B. Amin
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Florian Hofstätter
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Lydia L. Simpson
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Christopher Gasho
- Department of Medicine, Division of Pulmonary and Critical Care, University of Loma Linda, Loma Linda, California, USA
| | - Michael M. Tymko
- Physical Activity and Diabetes Laboratory, Faculty of Kinesiology, Sport and Recreation, University of Alberta, Edmonton, AB, Canada.,Centre of Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | - Philip N. Ainslie
- Centre of Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia – Okanagan, Kelowna, British Columbia, Canada
| | - Justin S. Lawley
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Christopher M. Hearon
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, TX, USA.,Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, TX, USA.,Correspondence: Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, 7232 Greenville Avenue, Suite 435, Dallas, TX, 75231, USA.
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15
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Ruggiero L, Harrison SWD, Rice CL, McNeil CJ. Neuromuscular fatigability at high altitude: Lowlanders with acute and chronic exposure, and native highlanders. Acta Physiol (Oxf) 2022; 234:e13788. [PMID: 35007386 PMCID: PMC9286620 DOI: 10.1111/apha.13788] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 01/04/2022] [Accepted: 01/05/2022] [Indexed: 01/18/2023]
Abstract
Ascent to high altitude is accompanied by a reduction in partial pressure of inspired oxygen, which leads to interconnected adjustments within the neuromuscular system. This review describes the unique challenge that such an environment poses to neuromuscular fatigability (peripheral, central and supraspinal) for individuals who normally reside near to sea level (SL) (<1000 m; ie, lowlanders) and for native highlanders, who represent the manifestation of high altitude-related heritable adaptations across millennia. Firstly, the effect of acute exposure to high altitude-related hypoxia on neuromuscular fatigability will be examined. Under these conditions, both supraspinal and peripheral fatigability are increased compared with SL. The specific mechanisms contributing to impaired performance are dependent on the exercise paradigm and amount of muscle mass involved. Next, the effect of chronic exposure to high altitude (ie, acclimatization of ~7-28 days) will be considered. With acclimatization, supraspinal fatigability is restored to SL values, regardless of the amount of muscle mass involved, whereas peripheral fatigability remains greater than SL except when exercise involves a small amount of muscle mass (eg, knee extensors). Indeed, when whole-body exercise is involved, peripheral fatigability is not different to acute high-altitude exposure, due to competing positive (haematological and muscle metabolic) and negative (respiratory-mediated) effects of acclimatization on neuromuscular performance. In the final section, we consider evolutionary adaptations of native highlanders (primarily Himalayans of Tibet and Nepal) that may account for their superior performance at altitude and lesser degree of neuromuscular fatigability compared with acclimatized lowlanders, for both single-joint and whole-body exercise.
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Affiliation(s)
- Luca Ruggiero
- Laboratory of Physiomechanics of LocomotionDepartment of Pathophysiology and TransplantationUniversity of MilanMilanItaly
| | - Scott W. D. Harrison
- School of KinesiologyFaculty of Health SciencesThe University of Western OntarioLondonOntarioCanada
| | - Charles L. Rice
- School of KinesiologyFaculty of Health SciencesThe University of Western OntarioLondonOntarioCanada
- Department of Anatomy and Cell BiologySchulich School of Medicine and DentistryThe University of Western OntarioLondonOntarioCanada
| | - Chris J. McNeil
- Centre for Heart, Lung & Vascular HealthSchool of Health and Exercise SciencesUniversity of British ColumbiaKelownaBritish ColumbiaCanada
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16
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Storz JF, Bautista NM. Altitude acclimatization, hemoglobin-oxygen affinity, and circulatory oxygen transport in hypoxia. Mol Aspects Med 2022; 84:101052. [PMID: 34879970 PMCID: PMC8821351 DOI: 10.1016/j.mam.2021.101052] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 11/12/2021] [Accepted: 11/15/2021] [Indexed: 01/01/2023]
Abstract
In mammals and other air-breathing vertebrates that live at high altitude, adjustments in convective O2 transport via changes in blood hemoglobin (Hb) content and/or Hb-O2 affinity can potentially mitigate the effects of arterial hypoxemia. However, there are conflicting views about the optimal values of such traits in hypoxia, partly due to the intriguing observation that hypoxia-induced acclimatization responses in humans and other predominantly lowland mammals are frequently not aligned in the same direction as evolved phenotypic changes in high-altitude natives. Here we review relevant theoretical and empirical results and we highlight experimental studies of rodents and humans that provide insights into the combination of hematological changes that help attenuate the decline in aerobic performance in hypoxia. For a given severity of hypoxia, experimental results suggest that optimal values for hematological traits are conditional on the states of other interrelated phenotypes that govern different steps in the O2-transport pathway.
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Affiliation(s)
- Jay F Storz
- School of Biological Sciences, University of Nebraska, Lincoln, NE, USA.
| | - Naim M Bautista
- School of Biological Sciences, University of Nebraska, Lincoln, NE, USA
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17
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Webb KL, Dominelli PB, Baker SE, Klassen SA, Joyner MJ, Senefeld JW, Wiggins CC. Influence of High Hemoglobin-Oxygen Affinity on Humans During Hypoxia. Front Physiol 2022; 12:763933. [PMID: 35095551 PMCID: PMC8795792 DOI: 10.3389/fphys.2021.763933] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 12/22/2021] [Indexed: 01/11/2023] Open
Abstract
Humans elicit a robust series of physiological responses to maintain adequate oxygen delivery during hypoxia, including a transient reduction in hemoglobin-oxygen (Hb-O2) affinity. However, high Hb-O2 affinity has been identified as a beneficial adaptation in several species that have been exposed to high altitude for generations. The observed differences in Hb-O2 affinity between humans and species adapted to high altitude pose a central question: is higher or lower Hb-O2 affinity in humans more advantageous when O2 availability is limited? Humans with genetic mutations in hemoglobin structure resulting in high Hb-O2 affinity have shown attenuated cardiorespiratory adjustments during hypoxia both at rest and during exercise, providing unique insight into this central question. Therefore, the purpose of this review is to examine the influence of high Hb-O2 affinity during hypoxia through comparison of cardiovascular and respiratory adjustments elicited by humans with high Hb-O2 affinity compared to those with normal Hb-O2 affinity.
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Affiliation(s)
- Kevin L. Webb
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, United States
| | | | - Sarah E. Baker
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, United States
| | - Stephen A. Klassen
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, United States
- Department of Kinesiology, Brock University, St. Catharines, ON, Canada
| | - Michael J. Joyner
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, United States
| | - Jonathon W. Senefeld
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, United States
| | - Chad C. Wiggins
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, United States
- *Correspondence: Chad C. Wiggins,
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18
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Burtscher M, Viscor G. How important is V̇O 2max when climbing Mt. Everest (8,849 m)? Respir Physiol Neurobiol 2021; 297:103833. [PMID: 34952230 DOI: 10.1016/j.resp.2021.103833] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Revised: 12/12/2021] [Accepted: 12/20/2021] [Indexed: 11/18/2022]
Abstract
The maximal rate of oxygen uptake (V̇O2max) of humans declines with increasing altitude, but represents the upper limit of aerobic endurance performance at low and high altitude as well. Before Reinhold Messner and Peter Habeler climbed Mt. Everest first (1978) without supplemental oxygen, physiologists have doubted whether this would be possible due to insufficient V̇O2max remaining when approaching the summit (8849 m). Subsequently, several studies evaluated the decline in the V̇O2max levels at real and simulated extreme altitudes. However, the potential influence of the preexisting individual sea level V̇O2max remained largely unconsidered. Based on available studies and case observations, here we discuss the observed and expected decline of V̇O2max up to 8849 m dependent on the individual sea level V̇O2max. It is concluded that a high sea level V̇O2max and an only moderate decline of arterial oxygen saturation and associated V̇O2max with increasing altitude, due to appropriate acclimatization and ascent strategies, enable certain mountaineers to climb 8,000er summits and even the Everest without supplemental oxygen.
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Affiliation(s)
- Martin Burtscher
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria.
| | - Ginés Viscor
- Physiology Section, Department of Cell Biology, Physiology and Immunology, Faculty of Biology, University of Barcelona, Barcelona, Spain
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19
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Pühringer R, Gatterer H, Berger M, Said M, Faulhaber M, Burtscher M. Does Moderate Altitude Affect VO 2max in Acclimatized Mountain Guides? High Alt Med Biol 2021; 23:37-42. [PMID: 34939827 DOI: 10.1089/ham.2021.0081] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Pühringer, Reinhard, Hannes Gatterer, Martin Berger, Michael Said, Martin Faulhaber, and Martin Burtscher. Does moderate altitude affect VO2max in acclimatized mountain guides? High Alt Med Biol 00:000-000, 2021. Background: Altitude exposure reduces maximal oxygen uptake (VO2max). Usually, the reduction is not restored with acclimatization (at least at altitudes above 2,500 m) and is more pronounced in highly trained athletes compared to nonathletes. It still remains to be elucidated whether these also apply for well-acclimatized individuals (i.e., mountain guides) acutely exposed to moderate altitude (i.e., 2,000 m). Methods: A total of 128 acclimatized male mountain guides of the Austrian armed forces (42.2 ± 7.0 years, 177.8 ± 5.6 cm, 77.2 ± 7.0 kg) of different fitness levels performed 2 incremental cycle ergometer tests 1 week apart, one at low (600 m) and one at moderate altitude (2,000 m). Oxygen uptake, heart rate (HR), and lactate concentration were measured during the tests. Results: In acclimatized mountain guides, lower baseline VO2max levels were associated with better preservation of VO2max at moderate altitude compared to higher levels. At moderate altitude, physiological responses (HR and blood lactate at 100 W) at a submaximal exercise intensity of 100 W remained unchanged or were even slightly reduced in both groups. Conclusions: Long-term acclimatization to moderate altitude may prevent the VO2max decline at a moderate altitude of 2,000 m particularly in subjects with lower VO2max levels, that is, below the 80th percentile (for age and sex). In people with higher fitness levels, VO2max may still be negatively affected. These results are of practical relevance, for example, for workers, athletes, ski and mountain guides, military staff, or rescue staff who regularly or continuously have to perform at moderate altitude.
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Affiliation(s)
- Reinhard Pühringer
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria.,Austrian Society for Alpine and Mountain Medicine, Innsbruck, Austria
| | - Hannes Gatterer
- Institute of Mountain Emergency Medicine, Eurac Research, Bolzano, Italy
| | - Martin Berger
- Department of Medicine, Military Hospital Innsbruck, Innsbruck, Austria
| | - Michael Said
- Department of Medicine, Military Hospital Innsbruck, Innsbruck, Austria
| | - Martin Faulhaber
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria.,Austrian Society for Alpine and Mountain Medicine, Innsbruck, Austria
| | - Martin Burtscher
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria.,Austrian Society for Alpine and Mountain Medicine, Innsbruck, Austria
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20
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Salvadego D, Grassi B, Keramidas ME, Eiken O, McDonnell AC, Mekjavic IB. Heterogeneity of human adaptations to bed rest and hypoxia: a retrospective analysis within the skeletal muscle oxidative function. Am J Physiol Regul Integr Comp Physiol 2021; 321:R813-R822. [PMID: 34585615 DOI: 10.1152/ajpregu.00053.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This retrospective study was designed to analyze the interindividual variability in the responses of different variables characterizing the skeletal muscle oxidative function to normoxic (N-BR) and hypoxic (H-BR) bed rests and to a hypoxic ambulatory confinement (H-AMB) of 10 and 21 days. We also assessed whether and how the addition of hypoxia to bed rest might influence the heterogeneity of the responses. In vivo measurements of O2 uptake and muscle fractional O2 extraction were carried out during an incremental one-leg knee-extension exercise. Mitochondrial respiration was assessed in permeabilized muscle fibers. A total of 17 subjects were included in this analysis. This analysis revealed a similar variability among subjects in the alterations induced by N-BR and H-BR both in peak O2 uptake (SD: 4.1% and 3.3% after 10 days; 4.5% and 8.1% after 21 days, respectively) and peak muscle fractional O2 extraction (SD: 5.9% and 7.3% after 10 days; 6.5% and 7.3% after 21 days), independently from the duration of the exposure. The individual changes measured in these variables were significantly related (r = 0.66, P = 0.004 after N-BR; r = 0.61, P = 0.009 after H-BR). Mitochondrial respiration showed a large variability of response after both N-BR (SD: 25.0% and 15.7% after 10 and 21 days) and H-BR (SD: 13.0% and 19.8% after 10 and 21 days); no correlation was found between N-BR and H-BR changes. When added to bed rest, hypoxia altered the individual adaptations within the mitochondria but not those intrinsic to the muscle oxidative function in vivo, both after the short- and medium-term exposures.
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Affiliation(s)
- Desy Salvadego
- Department of Automation, Biocybernetics and Robotics, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Bruno Grassi
- Department of Medicine, University of Udine, Udine, Italy
| | - Michail E Keramidas
- Department of Environmental Physiology, Swedish Aerospace Physiology Centre, Royal Institute of Technology, Stockholm, Sweden
| | - Ola Eiken
- Department of Environmental Physiology, Swedish Aerospace Physiology Centre, Royal Institute of Technology, Stockholm, Sweden
| | - Adam C McDonnell
- Department of Automation, Biocybernetics and Robotics, Jožef Stefan Institute, Ljubljana, Slovenia
| | - Igor B Mekjavic
- Department of Automation, Biocybernetics and Robotics, Jožef Stefan Institute, Ljubljana, Slovenia.,Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
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21
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Pooja, Sharma V, Meena RN, Ray K, Panjwani U, Varshney R, Sethy NK. TMT-Based Plasma Proteomics Reveals Dyslipidemia Among Lowlanders During Prolonged Stay at High Altitudes. Front Physiol 2021; 12:730601. [PMID: 34721061 PMCID: PMC8554329 DOI: 10.3389/fphys.2021.730601] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Accepted: 09/02/2021] [Indexed: 01/11/2023] Open
Abstract
Acute exposure to high altitude perturbs physiological parameters and induces an array of molecular changes in healthy lowlanders. However, activation of compensatory mechanisms and biological processes facilitates high altitude acclimatization. A large number of lowlanders stay at high altitude regions from weeks to months for work and professional commitments, and thus are vulnerable to altitude-associated disorders. Despite this, there is a scarcity of information for molecular changes associated with long-term stay at high altitudes. In the present study, we evaluated oxygen saturation (SpO2), heart rate (HR), and systolic and diastolic blood pressure (SBP and DBP) of lowlanders after short- (7 days, HA-D7) and long-term (3 months, HA-D150) stay at high altitudes, and used TMT-based proteomics studies to decipher plasma proteome alterations. We observed improvements in SpO2 levels after prolonged stay, while HR, SBP, and DBP remained elevated as compared with short-term stay. Plasma proteomics studies revealed higher levels of apolipoproteins APOB, APOCI, APOCIII, APOE, and APOL, and carbonic anhydrases (CA1 and CA2) during hypoxia exposure. Biological network analysis also identified profound alterations in lipoprotein-associated pathways like plasma lipoprotein assembly, VLDL clearance, chylomicron assembly, chylomicron remodeling, plasma lipoprotein clearance, and chylomicron clearance. In corroboration, lipid profiling revealed higher levels of total cholesterol (TC), triglycerides (TGs), low-density lipoprotein (LDL) for HA-D150 whereas high density lipoproteins (HDL) levels were lower as compared with HA-D7 and sea-level indicating dyslipidemia. We also observed higher levels of proinflammatory cytokines IL-6, TNFα, and CRP for HA-D150 along with oxidized LDL (oxLDL), suggesting vascular inflammation and proartherogenic propensity. These results demonstrate that long-term stay at high altitudes exacerbates dyslipidemia and associated disorders.
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Affiliation(s)
- Pooja
- Peptide and Proteomics Division, Defence Institute of Physiology and Allied Sciences, New Delhi, India
| | - Vandana Sharma
- Peptide and Proteomics Division, Defence Institute of Physiology and Allied Sciences, New Delhi, India
| | - Ram Niwas Meena
- Peptide and Proteomics Division, Defence Institute of Physiology and Allied Sciences, New Delhi, India
| | - Koushik Ray
- Neurophysiology Department, Defence Institute of Physiology and Allied Sciences, New Delhi, India
| | - Usha Panjwani
- Neurophysiology Department, Defence Institute of Physiology and Allied Sciences, New Delhi, India
| | - Rajeev Varshney
- Peptide and Proteomics Division, Defence Institute of Physiology and Allied Sciences, New Delhi, India
| | - Niroj Kumar Sethy
- Peptide and Proteomics Division, Defence Institute of Physiology and Allied Sciences, New Delhi, India
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22
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Forrer A, Scheiwiller PM, Mademilov M, Lichtblau M, Sheraliev U, Marazhapov NH, Saxer S, Bader P, Appenzeller P, Aydaralieva S, Muratbekova A, Sooronbaev TM, Ulrich S, Bloch KE, Furian M. Exercise Performance in Central Asian Highlanders: A Cross-Sectional Study. High Alt Med Biol 2021; 22:386-394. [PMID: 34432548 DOI: 10.1089/ham.2020.0211] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Forrer, Aglaia, Philipp M. Scheiwiller, Maamed Mademilov, Mona Lichtblau, Ulan Sheraliev, Nuriddin H. Marazhapov, Stéphanie Saxer, Patrick Bader, Paula Appenzeller, Shoira Aydaralieva, Aybermet Muratbekova, Talant M. Sooronbaev, Silvia Ulrich, Konrad E. Bloch, and Michael Furian. Exercise performance in central Asian highlanders: A cross-sectional study. High Alt Med Biol. 00:000-000, 2021. Introduction: Life-long exposure to hypobaric hypoxia induces physiologic adaptations in highlanders that may modify exercise performance; however, reference data for altitude populations are scant. Methods: Life-long residents of the Tien Shan mountain range, 2,500 - 3,500 m, Kyrgyzstan, free of cardiopulmonary disease, underwent cardiopulmonary cycle exercise tests with a progressive ramp protocol to exhaustion at 3,250 m. ECG, breath-by-breath pulmonary gas exchange, and oxygen saturation by pulse oximetry (SpO2) were measured. Results: Among 81 highlanders, age (mean ± SD) 48 ± 10 years, 46% women, SpO2 at rest was 88% ± 2%, peak oxygen uptake (V'O2peak) was 21.6 ± 5.9 mL/kg/min (76% ± 15% predicted for a low-altitude reference population); peak work rate (Wpeak) was 117 ± 37 W (77% ± 17% predicted), SpO2 at peak was 84% ± 5%, heart rate reserve (220 - age - maximal heart rate) was 28 ± 17/min, ventilatory reserve (maximal voluntary ventilation - maximal minute ventilation) was 68 ± 32 l/min, and respiratory exchange ratio was 1.03 ± 0.09. Peak BORG-CR10 dyspnea and leg fatigue scores were 5.1 ± 2.0 and 6.3 ± 2.1. In multivariable linear regression analyses, age and sex were robust determinants of Wpeak, V'O2peak, and metabolic equivalent (MET) at peak, whereas body mass index, resting systolic blood pressure, and mean pulmonary artery pressure were not. Conclusions: The current study shows that V'O2peak and Wpeak of highlanders studied at 3,250 m, near their altitude of residence, were reduced by about one quarter compared with mean predicted values for lowlanders. The provided prediction models for V'O2peak, Wpeak, and METs in central Asian highlanders might be valuable for comparisons with other high altitude populations.
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Affiliation(s)
- Aglaia Forrer
- Department of Respiratory Medicine, University Hospital of Zurich, Zurich, Switzerland.,Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic
| | - Philipp M Scheiwiller
- Department of Respiratory Medicine, University Hospital of Zurich, Zurich, Switzerland.,Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic
| | - Maamed Mademilov
- Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic.,Department of Respiratory Medicine, National Center for Cardiology and Internal Medicine, Bishkek, Kyrgyz Republic
| | - Mona Lichtblau
- Department of Respiratory Medicine, University Hospital of Zurich, Zurich, Switzerland.,Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic
| | - Ulan Sheraliev
- Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic.,Department of Respiratory Medicine, National Center for Cardiology and Internal Medicine, Bishkek, Kyrgyz Republic
| | - Nuriddin H Marazhapov
- Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic.,Department of Respiratory Medicine, National Center for Cardiology and Internal Medicine, Bishkek, Kyrgyz Republic
| | - Stéphanie Saxer
- Department of Respiratory Medicine, University Hospital of Zurich, Zurich, Switzerland.,Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic
| | - Patrick Bader
- Department of Respiratory Medicine, University Hospital of Zurich, Zurich, Switzerland.,Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic
| | - Paula Appenzeller
- Department of Respiratory Medicine, University Hospital of Zurich, Zurich, Switzerland.,Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic
| | - Shoira Aydaralieva
- Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic.,Department of Respiratory Medicine, National Center for Cardiology and Internal Medicine, Bishkek, Kyrgyz Republic
| | - Aybermet Muratbekova
- Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic.,Department of Respiratory Medicine, National Center for Cardiology and Internal Medicine, Bishkek, Kyrgyz Republic
| | - Talant M Sooronbaev
- Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic.,Department of Respiratory Medicine, National Center for Cardiology and Internal Medicine, Bishkek, Kyrgyz Republic
| | - Silvia Ulrich
- Department of Respiratory Medicine, University Hospital of Zurich, Zurich, Switzerland.,Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic
| | - Konrad E Bloch
- Department of Respiratory Medicine, University Hospital of Zurich, Zurich, Switzerland.,Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic
| | - Michael Furian
- Department of Respiratory Medicine, University Hospital of Zurich, Zurich, Switzerland.,Swiss-Kyrgyz High Altitude Medicine and Research Initiative, Zurich, Switzerland, and Bishkek, Kyrgyz Republic
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23
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Jacobs RA, Lundby C. Contextualizing the biological relevance of standardized high-resolution respirometry to assess mitochondrial function in permeabilized human skeletal muscle. Acta Physiol (Oxf) 2021; 231:e13625. [PMID: 33570804 PMCID: PMC8047922 DOI: 10.1111/apha.13625] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 02/08/2021] [Accepted: 02/09/2021] [Indexed: 12/16/2022]
Abstract
Aim This study sought to provide a statistically robust reference for measures of mitochondrial function from standardized high‐resolution respirometry with permeabilized human skeletal muscle (ex vivo), compare analogous values obtained via indirect calorimetry, arterial‐venous O2 differences and 31P magnetic resonance spectroscopy (in vivo) and attempt to resolve differences across complementary methodologies as necessary. Methods Data derived from 831 study participants across research published throughout March 2009 to November 2019 were amassed to examine the biological relevance of ex vivo assessments under standard conditions, ie physiological temperatures of 37°C and respiratory chamber oxygen concentrations of ~250 to 500 μmol/L. Results Standard ex vivo‐derived measures are lower (Z ≥ 3.01, P ≤ .0258) en masse than corresponding in vivo‐derived values. Correcting respiratory values to account for mitochondrial temperatures 10°C higher than skeletal muscle temperatures at maximal exercise (~50°C): (i) transforms data to resemble (Z ≤ 0.8, P > .9999) analogous yet context‐specific in vivo measures, eg data collected during maximal 1‐leg knee extension exercise; and (ii) supports the position that maximal skeletal muscle respiratory rates exceed (Z ≥ 13.2, P < .0001) those achieved during maximal whole‐body exercise, e.g. maximal cycling efforts. Conclusion This study outlines and demonstrates necessary considerations when actualizing the biological relevance of human skeletal muscle respiratory control, metabolic flexibility and bioenergetics from standard ex vivo‐derived assessments using permeabilized human muscle. These findings detail how cross‐procedural comparisons of human skeletal muscle mitochondrial function may be collectively scrutinized in their relationship to human health and lifespan.
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Affiliation(s)
- Robert A. Jacobs
- Department of Human Physiology & Nutrition University of Colorado Colorado Springs (UCCS) Colorado Springs CO USA
| | - Carsten Lundby
- Innland University of Applied Sciences Lillehammer Norway
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24
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Storz JF. High-Altitude Adaptation: Mechanistic Insights from Integrated Genomics and Physiology. Mol Biol Evol 2021; 38:2677-2691. [PMID: 33751123 PMCID: PMC8233491 DOI: 10.1093/molbev/msab064] [Citation(s) in RCA: 56] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Population genomic analyses of high-altitude humans and other vertebrates have identified numerous candidate genes for hypoxia adaptation, and the physiological pathways implicated by such analyses suggest testable hypotheses about underlying mechanisms. Studies of highland natives that integrate genomic data with experimental measures of physiological performance capacities and subordinate traits are revealing associations between genotypes (e.g., hypoxia-inducible factor gene variants) and hypoxia-responsive phenotypes. The subsequent search for causal mechanisms is complicated by the fact that observed genotypic associations with hypoxia-induced phenotypes may reflect second-order consequences of selection-mediated changes in other (unmeasured) traits that are coupled with the focal trait via feedback regulation. Manipulative experiments to decipher circuits of feedback control and patterns of phenotypic integration can help identify causal relationships that underlie observed genotype–phenotype associations. Such experiments are critical for correct inferences about phenotypic targets of selection and mechanisms of adaptation.
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Affiliation(s)
- Jay F Storz
- School of Biological Sciences, University of Nebraska, Lincoln, NE, USA
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25
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Holmström PK, Bird JD, Thrall SF, Kalker A, Herrington BA, Soriano JE, Mann LM, Rampuri ZH, Brutsaert TD, Karlsson Ø, Sherpa MT, Schagatay EKA, Day TA. The effects of high altitude ascent on splenic contraction and the diving response during voluntary apnoea. Exp Physiol 2020; 106:160-174. [DOI: 10.1113/ep088571] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 09/03/2020] [Indexed: 12/30/2022]
Affiliation(s)
| | - Jordan D. Bird
- Department of Biology Faculty of Science and Technology Mount Royal University Calgary Alberta Canada
| | - Scott F. Thrall
- Department of Biology Faculty of Science and Technology Mount Royal University Calgary Alberta Canada
| | - Ann Kalker
- Department of Biology Faculty of Science and Technology Mount Royal University Calgary Alberta Canada
- Radboud University Nijmegen Netherlands
| | - Brittney A. Herrington
- Department of Biology Faculty of Science and Technology Mount Royal University Calgary Alberta Canada
| | - Jan E. Soriano
- Department of Biology Faculty of Science and Technology Mount Royal University Calgary Alberta Canada
| | - Leah M. Mann
- Department of Biology Faculty of Science and Technology Mount Royal University Calgary Alberta Canada
| | - Zahrah H. Rampuri
- Department of Biology Faculty of Science and Technology Mount Royal University Calgary Alberta Canada
| | - Tom D. Brutsaert
- Department of Exercise Science Syracuse University Syracuse NY USA
| | - Øyvind Karlsson
- Swedish Winter Sports Research Centre Mid Sweden University Östersund Sweden
| | | | - Erika K. A. Schagatay
- Department of Health Sciences Mid Sweden University Östersund Sweden
- Swedish Winter Sports Research Centre Mid Sweden University Östersund Sweden
| | - Trevor A. Day
- Department of Biology Faculty of Science and Technology Mount Royal University Calgary Alberta Canada
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26
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Mairbäurl H, Gassmann M, Muckenthaler MU. Geographical ancestry affects normal hemoglobin values in high-altitude residents. J Appl Physiol (1985) 2020; 129:1451-1459. [PMID: 33002380 DOI: 10.1152/japplphysiol.00025.2020] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Increasing the hemoglobin (Hb) concentration is a major mechanism adjusting arterial oxygen content to decreased oxygen partial pressure of inspired air at high altitude. Approximately 5% of the world's population living at altitudes higher than 1,500 m shows this adaptive mechanism. Notably, there is a wide variation in the extent of increase in Hb concentration among different populations. This short review summarizes available information on Hb concentrations of high-altitude residents living at comparable altitudes (3,500-4,500 m) in different regions of the world. An increased Hb concentration is found in all high-altitude populations. The highest mean Hb concentration was found in adult male Andean residents and in Han Chinese living at high altitude, whereas it was lowest in Ethiopians, Tibetans, and Sherpas. A lower plasma volume in Andean high-altitude natives may offer a partial explanation. Indeed, male Andean high-altitude natives have a lower plasma volume than Tibetans and Ethiopians. Moreover, Hb values were lower in adult, nonpregnant females than in males; differences between populations of different ancestry were less pronounced. Various genetic polymorphisms were detected in high-altitude residents thought to favor life in a hypoxic environment, some of which correlate with the relatively low Hb concentration in the Tibetans and Ethiopians, whereas differences in angiotensin-converting enzyme allele distribution may be related to elevated Hb in the Andeans. Taken together, these results indicate different sensitivity of oxygen dependent control of erythropoiesis or plasma volume among populations of different geographical ancestry, offering explanations for differences in the Hb concentration at high altitude.
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Affiliation(s)
- Heimo Mairbäurl
- Departmment of Translational Pneumology, University Hospital Heidelberg, Heidelberg, Germany.,Translational Lung Research Center Heidelberg, Member of the German Center for Lung Research, Heidelberg, Germany
| | - Max Gassmann
- Vetsuisse Faculty, Institute of Veterinary Physiology, University of Zurich, Zurich, Switzerland.,Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.,Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Martina U Muckenthaler
- Translational Lung Research Center Heidelberg, Member of the German Center for Lung Research, Heidelberg, Germany.,Departmment of Pediatric Hematology, Oncology and Immunology, University Hospital Heidelberg, Heidelberg, Germany.,Molecular Medicine Partnership Unit, University of Heidelberg, Heidelberg, Germany.,German Centre for Cardiovascular Research, Partner Site Heidelberg/Mannheim, Germany
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27
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Skattebo Ø, Calbet JAL, Rud B, Capelli C, Hallén J. Contribution of oxygen extraction fraction to maximal oxygen uptake in healthy young men. Acta Physiol (Oxf) 2020; 230:e13486. [PMID: 32365270 PMCID: PMC7540168 DOI: 10.1111/apha.13486] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 04/22/2020] [Accepted: 04/23/2020] [Indexed: 12/16/2022]
Abstract
We analysed the importance of systemic and peripheral arteriovenous O2 difference (
a-v¯O2 difference and a‐vfO2 difference, respectively) and O2 extraction fraction for maximal oxygen uptake (
V˙O2max). Fick law of diffusion and the Piiper and Scheid model were applied to investigate whether diffusion versus perfusion limitations vary with
V˙O2max. Articles (n = 17) publishing individual data (n = 154) on
V˙O2max, maximal cardiac output (
Q˙max; indicator‐dilution or the Fick method),
a-v¯O2 difference (catheters or the Fick equation) and systemic O2 extraction fraction were identified. For the peripheral responses, group‐mean data (articles: n = 27; subjects: n = 234) on leg blood flow (LBF; thermodilution), a‐vfO2 difference and O2 extraction fraction (arterial and femoral venous catheters) were obtained.
Q˙max and two‐LBF increased linearly by 4.9‐6.0 L · min–1 per 1 L · min–1 increase in
V˙O2max (R2 = .73 and R2 = .67, respectively; both P < .001). The
a-v¯O2 difference increased from 118‐168 mL · L–1 from a
V˙O2max of 2‐4.5 L · min–1 followed by a reduction (second‐order polynomial: R2 = .27). After accounting for a hypoxemia‐induced decrease in arterial O2 content with increasing
V˙O2max (R2 = .17; P < .001), systemic O2 extraction fraction increased up to ~90% (
V˙O2max: 4.5 L · min–1) with no further change (exponential decay model: R2 = .42). Likewise, leg O2 extraction fraction increased with
V˙O2max to approach a maximal value of ~90‐95% (R2 = .83). Muscle O2 diffusing capacity and the equilibration index Y increased linearly with
V˙O2max (R2 = .77 and R2 = .31, respectively; both P < .01), reflecting decreasing O2 diffusional limitations and accentuating O2 delivery limitations. In conclusion, although O2 delivery is the main limiting factor to
V˙O2max, enhanced O2 extraction fraction (≥90%) contributes to the remarkably high
V˙O2max in endurance‐trained individuals.
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Affiliation(s)
- Øyvind Skattebo
- Department of Physical Performance Norwegian School of Sport Sciences Oslo Norway
| | - Jose A. L. Calbet
- Department of Physical Performance Norwegian School of Sport Sciences Oslo Norway
- Department of Physical Education and Research Institute of Biomedical and Health Sciences (IUIBS) University of Las Palmas de Gran Canaria Gran Canaria Spain
| | - Bjarne Rud
- Department of Physical Performance Norwegian School of Sport Sciences Oslo Norway
| | - Carlo Capelli
- Department of Physical Performance Norwegian School of Sport Sciences Oslo Norway
- Department of Neurosciences, Biomedicine and Movement Sciences University of Verona Verona Italy
| | - Jostein Hallén
- Department of Physical Performance Norwegian School of Sport Sciences Oslo Norway
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28
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Muckenthaler MU, Mairbäurl H, Gassmann M. Iron metabolism in high-altitude residents. J Appl Physiol (1985) 2020; 129:920-925. [PMID: 32853112 DOI: 10.1152/japplphysiol.00019.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Residents at high altitude cope with decreasing inspiratory oxygen partial pressure by stimulating erythropoiesis. The increase in hemoglobin levels requires high amounts of additional iron supplied from the diet. Here, we review available data on how iron metabolism adapts when living in a hypoxic environment. Our analysis reveals that long-term adaptation to high altitude enables healthy individuals to maintain their iron stores within the physiological range despite elevated requirements for erythropoiesis. However, in vulnerable populations with increased iron demand (e.g., pregnant women or exercising individuals), iron stores are less likely to be replenished quickly when living at high altitude. Future studies need to address whether different ethnicities have acquired genetic mechanisms to adapt to the elevated iron demand for erythropoiesis at high altitude.
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Affiliation(s)
- Martina U Muckenthaler
- Pediatric Oncology, Hematology & Immunology, University Hospital Heidelberg, Heidelberg, Molecular Medicine Partnership Unit, University of Heidelberg, Heidelberg, Germany.,Translational Lung Research Center Heidelberg, Member of the German Center for Lung Research, Heidelberg, Germany
| | - Heimo Mairbäurl
- Translational Lung Research Center Heidelberg, Member of the German Center for Lung Research, Heidelberg, Germany.,Translational Pneumology, University Hospital Heidelberg, Heidelberg, Germany
| | - Max Gassmann
- Institute of Veterinary Physiology, Vetsuisse Faculty, and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland.,Universidad Peruana Cayetano Heredia, Lima, Peru
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29
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Dawson NJ, Alza L, Nandal G, Scott GR, McCracken KG. Convergent changes in muscle metabolism depend on duration of high-altitude ancestry across Andean waterfowl. eLife 2020; 9:e56259. [PMID: 32729830 PMCID: PMC7494360 DOI: 10.7554/elife.56259] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 07/23/2020] [Indexed: 01/07/2023] Open
Abstract
High-altitude environments require that animals meet the metabolic O2 demands for locomotion and thermogenesis in O2-thin air, but the degree to which convergent metabolic changes have arisen across independent high-altitude lineages or the speed at which such changes arise is unclear. We examined seven high-altitude waterfowl that have inhabited the Andes (3812-4806 m elevation) over varying evolutionary time scales, to elucidate changes in biochemical pathways of energy metabolism in flight muscle relative to low-altitude sister taxa. Convergent changes across high-altitude taxa included increased hydroxyacyl-coA dehydrogenase and succinate dehydrogenase activities, decreased lactate dehydrogenase, pyruvate kinase, creatine kinase, and cytochrome c oxidase activities, and increased myoglobin content. ATP synthase activity increased in only the longest established high-altitude taxa, whereas hexokinase activity increased in only newly established taxa. Therefore, changes in pathways of lipid oxidation, glycolysis, and mitochondrial oxidative phosphorylation are common strategies to cope with high-altitude hypoxia, but some changes require longer evolutionary time to arise.
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Affiliation(s)
- Neal J Dawson
- Department of Biology, McMaster UniversityHamiltonCanada
- Department of Biology University of MiamiCoral GablesUnited States
| | - Luis Alza
- Department of Biology University of MiamiCoral GablesUnited States
- University of Alaska Museum and Institute of Arctic Biology, University of Alaska FairbanksFairbanksUnited States
- Centro de Ornitología y Biodiversidad - CORBIDILimaPeru
| | | | - Graham R Scott
- Department of Biology, McMaster UniversityHamiltonCanada
| | - Kevin G McCracken
- Department of Biology University of MiamiCoral GablesUnited States
- University of Alaska Museum and Institute of Arctic Biology, University of Alaska FairbanksFairbanksUnited States
- Centro de Ornitología y Biodiversidad - CORBIDILimaPeru
- Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Sciences, University of MiamiMiamiUnited States
- Human Genetics and Genomics, Hussman Institute for Human Genomics, University of Miami Miller School of MedicineMiamiUnited States
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30
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Marillier M, Rupp T, Bouzat P, Walther G, Baillieul S, Millet GY, Robach P, Verges S. Cerebral haemodynamics and oxygenation during whole‐body exercise over 5 days at high altitude. Exp Physiol 2020; 106:65-75. [DOI: 10.1113/ep088354] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Accepted: 01/27/2020] [Indexed: 11/08/2022]
Affiliation(s)
- Mathieu Marillier
- HP2 Laboratory INSERM Grenoble Alpes University CHU Grenoble Alpes Grenoble France
| | - Thomas Rupp
- HP2 Laboratory INSERM Grenoble Alpes University CHU Grenoble Alpes Grenoble France
- Inter‐University Laboratory of Human Movement Sciences EA 7424 University Savoie Mont Blanc Chambery France
| | - Pierre Bouzat
- Grenoble Institute of Neurosciences INSERM U836 Grenoble Alpes University Grenoble France
| | | | - Sébastien Baillieul
- HP2 Laboratory INSERM Grenoble Alpes University CHU Grenoble Alpes Grenoble France
| | - Guillaume Y. Millet
- HP2 Laboratory INSERM Grenoble Alpes University CHU Grenoble Alpes Grenoble France
- Univ Lyon UJM‐Saint‐Etienne Laboratoire Interuniversitaire de Biologie de la Motricité EA 7424 F‐42023 Saint‐Etienne France
| | - Paul Robach
- HP2 Laboratory INSERM Grenoble Alpes University CHU Grenoble Alpes Grenoble France
- Ecole Nationale des Sports de Montagne site de l'Ecole Nationale de Ski et d'Alpinisme Chamonix France
| | - Samuel Verges
- HP2 Laboratory INSERM Grenoble Alpes University CHU Grenoble Alpes Grenoble France
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Azevedo RDA, Béjar Saona JE, Inglis EC, Iannetta D, Murias JM. The effect of the fraction of inspired oxygen on the NIRS-derived deoxygenated hemoglobin "breakpoint" during ramp-incremental test. Am J Physiol Regul Integr Comp Physiol 2019; 318:R399-R409. [PMID: 31850819 DOI: 10.1152/ajpregu.00291.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
During ramp-incremental (RI) exercise to exhaustion, the near-infrared spectroscopy-derived deoxygenated hemoglobin ([HHb]) signal in the vastus lateralis muscle shows a linear increase up to a point at which a plateau-like response is manifested ([HHb]bp). This study investigated if 1) the [HHb]bp is affected by different fractions of inspired O2 (FIO2) [hypoxia (16%; HYPO); normoxia (21%; NORM); hyperoxia (30%; HYPER)]; and 2) an abrupt change to hyperoxic-inspired gas just before the occurrence of the [HHb]bp (HYPERSWITCH) would affect the [HHb] plateau-like response. Ten physically active male participants reported to the laboratory on four separate occasions to perform an RI test to exhaustion in NORM, HYPO, and HYPER and an RI test to exhaustion with an abrupt increase in FIO2 (30%; HYPERSWITCH) 15 W before the power output (PO) associated with [HHb]bp in normoxia. PO, [HHb], tissue O2 (StO2), and pulse O2 saturation (SpO2) were recorded continuously. Peak PO was significantly lower in HYPO (290 ± 21 W) and higher in HYPER (321 ± 22 W) and HYPERSWITCH (320 ± 19 W) compared with NORM (311 ± 18 W). The PO associated with [HHb]bp was not different between NORM and HYPER (246 ± 23 vs. 247 ± 24 W), but it was lower in HYPO (198 ± 31 W) than NORM and HYPER. The PO associated with the [HHb]bp in HYPERSWITCH (240 ± 23) was not different compared with NORM. HYPER and HYPERSWITCH resulted in greater StO2 and SpO2 compared with NORM. These results suggest that the [HHb]bp response is not dependent of O2 driving pressure and that other physiological mechanisms might determine its occurrence.
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Affiliation(s)
| | | | | | - Danilo Iannetta
- Faculty of Kinesiology, University of Calgary, Calgary, Canada
| | - Juan M Murias
- Faculty of Kinesiology, University of Calgary, Calgary, Canada
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Mairbäurl H. Kinetics of Changes in Hemoglobin After Ascent to and Return from High Altitude. ACTA ACUST UNITED AC 2019. [DOI: 10.1007/s42978-019-00044-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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No ergogenic effects of a 10-day combined heat and hypoxic acclimation on aerobic performance in normoxic thermoneutral or hot conditions. Eur J Appl Physiol 2019; 119:2513-2527. [PMID: 31555926 DOI: 10.1007/s00421-019-04215-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 08/21/2019] [Indexed: 10/25/2022]
Abstract
PURPOSE Hypoxic acclimation enhances convective oxygen delivery to the muscles. Heat acclimation-elicited thermoregulatory benefits have been suggested not to be negated by adding daily exposure to hypoxia. Whether concomitant acclimation to both heat and hypoxia offers a synergistic enhancement of aerobic performance in thermoneutral or hot conditions remains unresolved. METHODS Eight young males ([Formula: see text]: 51.6 ± 4.6 mL min-1 kg-1) underwent a 10-day normobaric hypoxic confinement (FiO2 = 0.14) interspersed with daily 90-min normoxic controlled hyperthermia (target rectal temperature: 38.5 °C) exercise sessions. Prior to, and following the confinement, the participants conducted a 30-min steady-state exercise followed by incremental exercise to exhaustion on a cycle ergometer in thermoneutral normoxic (NOR), thermoneutral hypoxic (FiO2 = 0.14; HYP) and hot (35 °C, 50% relative humidity; HE) conditions in a randomized and counterbalanced order. The steady-state exercise was performed at 40% NOR peak power output (Wpeak) to evaluate thermoregulatory function. Blood samples were obtained from an antecubital vein before, on days 1 and 10, and the first day post-acclimation. RESULTS [Formula: see text] and ventilatory thresholds were not modified in any environment following acclimation. Wpeak increased by 6.3 ± 3.4% in NOR and 4.0 ± 4.9% in HE, respectively. The magnitude and gain of the forehead sweating response were augmented in HE post-acclimation. EPO increased from baseline (17.8 ± 7.0 mIU mL-1) by 10.7 ± 8.8 mIU mL-1 on day 1 but returned to baseline levels by day 10 (15.7 ± 5.9 mIU mL-1). DISCUSSION A 10-day combined heat and hypoxic acclimation conferred only minor benefits in aerobic performance and thermoregulation in thermoneutral or hot conditions. Thus, adoption of such a protocol does not seem warranted.
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Moraga FA, Osorio J, Jiménez D, Calderón-Jofré R, Moraga D. Aerobic Capacity, Lactate Concentration, and Work Assessment During Maximum Exercise at Sea Level and High Altitude in Miners Exposed to Chronic Intermittent Hypobaric Hypoxia (3,800 m). Front Physiol 2019; 10:1149. [PMID: 31555155 PMCID: PMC6742696 DOI: 10.3389/fphys.2019.01149] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 08/26/2019] [Indexed: 12/01/2022] Open
Abstract
We previously showed that arterial oxygen content during maximum exercise remains constant at high altitude (HA) in miners exposed to chronic intermittent hypobaric hypoxia (CIHH). Nevertheless, information about VO2, lactate concentration [Lac], and work efficiency are absent in this CIHH miner population. Our aim was to determine aerobic capacity, [Lac], and work efficiency at sea level (SL) and HA during maximum exercise in miners acclimatized to CIHH at 3,800 m. Eight volunteer miners acclimatized to CIHH at HA (> 4 years) performed an exercise test at SL and HA. The test was performed on the 4th day at HA or SL and consisted of three phases: Rest (5 min); Exercise test, where the load was increased by 50 W every 3 min until exhaustion; and a Recovery period of 30 min. During the procedure VO2, transcutaneous arterial saturation (SpO2, %), and HR (bpm) were assessed at each step by a pulse oximeter and venous blood samples were taken to measure [Lac] and hemoglobin concentration. No differences in VO2 and [Lac] in SL vs. HA were observed in this CIHH miner population. By contrast, a higher HR and lower SpO2 were observed at SL compared with HA. During maximum exercise, a reduction in VO2 and [Lac] was observed without differences in intensity (W) and HR. A decrease in [Lac] was observed at maximum effort (250 W) and recovery at HA vs. SL. These findings are related to an increased work efficiency assessment such as gross and net efficiency. This study is the first to show that miners exposed to CIHH maintain their work capacity (intensity) with a fall in oxygen consumption and a decrease in plasmatic lactate concentration at maximal effort at HA. These findings indicate that work efficiency at HA is enhanced.
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Affiliation(s)
- Fernando A Moraga
- Laboratorio de Fisiología, Hipoxia y Función Vascular, Departamento de Ciencias Biomédicas, Facultad de Medicina, Universidad Católica del Norte, Coquimbo, Chile
| | - Jorge Osorio
- Instituto de Estudios de la Salud, Universidad Arturo Prat, Iquique, Chile
| | - Daniel Jiménez
- Escuela de Salud Pública, Facultad de Medicina, Universidad de Chile, Santiago, Chile
| | - Rodrigo Calderón-Jofré
- Laboratorio de Fisiología, Hipoxia y Función Vascular, Departamento de Ciencias Biomédicas, Facultad de Medicina, Universidad Católica del Norte, Coquimbo, Chile.,Departamento de Ciencias Básicas, Universidad Santo Tomás, La Serena, Chile
| | - Daniel Moraga
- Carrera de Medicina, Facultad de Ciencias de la Salud, Universidad de Tarapacá, Arica, Chile
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Holmström P, Mulder E, Sundström AL, Limbu P, Schagatay E. The Magnitude of Diving Bradycardia During Apnea at Low-Altitude Reveals Tolerance to High Altitude Hypoxia. Front Physiol 2019; 10:1075. [PMID: 31507443 PMCID: PMC6714063 DOI: 10.3389/fphys.2019.01075] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 08/05/2019] [Indexed: 11/13/2022] Open
Abstract
Acute mountain sickness (AMS) is a potentially life-threatening illness that may develop during exposure to hypoxia at high altitude (HA). Susceptibility to AMS is highly individual, and the ability to predict it is limited. Apneic diving also induces hypoxia, and we aimed to investigate whether protective physiological responses, i.e., the cardiovascular diving response and spleen contraction, induced during apnea at low-altitude could predict individual susceptibility to AMS. Eighteen participants (eight females) performed three static apneas in air, the first at a fixed limit of 60 s (A1) and two of maximal duration (A2-A3), spaced by 2 min, while SaO2, heart rate (HR) and spleen volume were measured continuously. Tests were conducted in Kathmandu (1470 m) before a 14 day trek to mount Everest Base Camp (5360 m). During the trek, participants reported AMS symptoms daily using the Lake Louise Questionnaire (LLQ). The apnea-induced HR-reduction (diving bradycardia) was negatively correlated with the accumulated LLQ score in A1 (r s = -0.628, p = 0.005) and A3 (r s = -0.488, p = 0.040) and positively correlated with SaO2 at 4410 m (A1: r = 0.655, p = 0.003; A2: r = 0.471, p = 0.049; A3: r = 0.635, p = 0.005). Baseline spleen volume correlated negatively with LLQ score (r s = -0.479, p = 0.044), but no correlation was found between apnea-induced spleen volume reduction with LLQ score (r s = 0.350, p = 0.155). The association between the diving bradycardia and spleen size with AMS symptoms suggests links between physiological responses to HA and apnea. Measuring individual responses to apnea at sea-level could provide means to predict AMS susceptibility prior to ascent.
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Affiliation(s)
- Pontus Holmström
- Department of Health Sciences, Mid Sweden University, Sundsvall, Sweden
| | - Eric Mulder
- Department of Health Sciences, Mid Sweden University, Sundsvall, Sweden
| | | | - Prakash Limbu
- Department of Clinical Physiology, Nepalese Army Institute of Health Sciences, Kathmandu, Nepal
| | - Erika Schagatay
- Department of Health Sciences, Mid Sweden University, Sundsvall, Sweden
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Kicken CH, van der Vorm LN, Zwaveling S, Schoenmaker E, Remijn JA, Huskens D, de Laat B. A Hypoxic Environment Attenuates Exercise-Induced Procoagulant Changes Due to Decreased Platelet Activation. TH OPEN 2019; 3:e216-e226. [PMID: 31338487 PMCID: PMC6645913 DOI: 10.1055/s-0039-1692991] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 05/23/2019] [Indexed: 02/06/2023] Open
Abstract
Introduction Although physical exercise is protective against cardiovascular disease, it can also provoke sudden cardiac death (exercise paradox). Epidemiological studies suggest that systemic hypoxia at high altitude is a risk factor for venous thromboembolism. Forthcoming, this study investigated the effect of repeated exercise at high altitude on blood coagulation, platelet function, and fibrinolysis. Methods Six trained male volunteers were recruited. Participants ascended from sea level to 3,375 m altitude. They performed four exercise tests at 65 to 80% of their heart-rate reserve during 2 hours: one time at sea level and three times on consecutive days at 3,375 m altitude. Thrombin generation (TG) was measured in whole blood (WB) and platelet-rich and platelet-poor plasma. Coagulation factor levels were measured. Platelet activation was measured as αIIbβ3 activation and P-selectin expression. Fibrinolysis was studied using a clot-lysis assay. Results Normoxic exercise increased plasma peak TG through increased factor VIII (FVIII), and increased von Willebrand factor (VWF) and active VWF levels. Platelet granule release potential was slightly decreased. After repetitive hypoxic exercise, the increase in (active) VWF tapered, and there was no more distinct exercise-related increase in peak. Platelet aggregation potential and platelet-dependent TG decreased at high altitude. There were no effects on fibrinolysis upon exercise and/or hypoxia. Conclusion Strenuous exercise induces a procoagulant state that is mediated by the endothelium, by increasing VWF and secondarily raising FVIII levels. After repetitive exercise, the amplitude of the endothelial response to exercise diminishes. A hypoxic environment appears to further attenuate the procoagulant changes by decreasing platelet activation and platelet-dependent TG.
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Affiliation(s)
- Cécile H. Kicken
- Department of Anesthesiology, Maastricht University Medical Center, Maastricht, The Netherlands
- Synapse Research Institute, Maastricht, The Netherlands
| | - Lisa N. van der Vorm
- Synapse Research Institute, Maastricht, The Netherlands
- Department of Clinical Chemistry and Hematology, Gelre Hospitals, Apeldoorn, The Netherlands
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
| | - Suzanne Zwaveling
- Synapse Research Institute, Maastricht, The Netherlands
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
| | | | - Jasper A. Remijn
- Department of Clinical Chemistry and Hematology, Gelre Hospitals, Apeldoorn, The Netherlands
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
- Department of Clinical Chemistry, Meander Medical Center, Amersfoort, The Netherlands
| | - Dana Huskens
- Synapse Research Institute, Maastricht, The Netherlands
| | - Bas de Laat
- Synapse Research Institute, Maastricht, The Netherlands
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
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Gassmann M, Mairbäurl H, Livshits L, Seide S, Hackbusch M, Malczyk M, Kraut S, Gassmann NN, Weissmann N, Muckenthaler MU. The increase in hemoglobin concentration with altitude varies among human populations. Ann N Y Acad Sci 2019; 1450:204-220. [PMID: 31257609 DOI: 10.1111/nyas.14136] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 05/02/2019] [Accepted: 05/16/2019] [Indexed: 02/06/2023]
Abstract
Decreased oxygen availability at high altitude requires physiological adjustments allowing for adequate tissue oxygenation. One such mechanism is a slow increase in the hemoglobin concentration ([Hb]) resulting in elevated [Hb] in high-altitude residents. Diagnosis of anemia at different altitudes requires reference values for [Hb]. Our aim was to establish such values based on published data of residents living at different altitudes by applying meta-analysis and multiple regressions. Results show that [Hb] is increased in all high-altitude residents. However, the magnitude of increase varies among the regions analyzed and among ethnic groups within a region. The highest increase was found in residents of the Andes (1 g/dL/1000 m), but this increment was smaller in all other regions of the world (0.6 g/dL/1000 m). While sufficient data exist for adult males and females showing that sex differences in [Hb] persist with altitude, data for infants, children, and pregnant women are incomplete preventing such analyses. Because WHO reference values were originally based on [Hb] of South American people, we conclude that individual reference values have to be defined for ethnic groups to reliably diagnose anemia and erythrocytosis in high-altitude residents. Future studies need to test their applicability for children of different ages and pregnant women.
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Affiliation(s)
- Max Gassmann
- Institute of Veterinary Physiology, Vetsuisse Faculty and Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland.,Universidad Peruana Cayetano Heredia (UPCH), Lima, Peru
| | - Heimo Mairbäurl
- Translational Lung Research Center Heidelberg (TLRC), the German Center for Lung Research (DZL), Heidelberg, Germany
| | - Leonid Livshits
- Institute of Veterinary Physiology, Vetsuisse Faculty and Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland
| | - Svenja Seide
- Institute of Medical Biometry and Informatics (IMBI), University Hospital Heidelberg, Heidelberg, Germany
| | - Matthes Hackbusch
- Institute of Medical Biometry and Informatics (IMBI), University Hospital Heidelberg, Heidelberg, Germany
| | - Monika Malczyk
- Excellence Cluster Cardiopulmonary System, Justus-Liebig-University Giessen, University of Giessen and Marburg Lung Center, German Center for Lung Research (DZL), Heidelberg, Germany
| | - Simone Kraut
- Excellence Cluster Cardiopulmonary System, Justus-Liebig-University Giessen, University of Giessen and Marburg Lung Center, German Center for Lung Research (DZL), Heidelberg, Germany
| | - Norina N Gassmann
- Institute of Veterinary Physiology, Vetsuisse Faculty and Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland
| | - Norbert Weissmann
- Excellence Cluster Cardiopulmonary System, Justus-Liebig-University Giessen, University of Giessen and Marburg Lung Center, German Center for Lung Research (DZL), Heidelberg, Germany
| | - Martina U Muckenthaler
- Pediatric Hematology, Oncology and Immunology, University Hospital Heidelberg, Molecular Medicine Partnership Unit, University of Heidelberg, Translational Lung Research Center Heidelberg (TLRC), German Center for Lung Research, Heidelberg, Germany
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Mahon RT, Ciarlone GE, Roney NG, Swift JM. Cardiovascular Parameters in a Swine Model of Normobaric Hypoxia Treated With 5-Hydroxymethyl-2-Furfural (5-HMF). Front Physiol 2019; 10:395. [PMID: 31057414 PMCID: PMC6482156 DOI: 10.3389/fphys.2019.00395] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2018] [Accepted: 03/21/2019] [Indexed: 11/24/2022] Open
Abstract
Introduction: The consequences of low partial pressure of O2 include low arterial O2 saturations (SaO2), low blood O2 content (CaO2), elevated mean pulmonary artery pressure (PAP), and decreased O2 consumption VO2. 5-hydroxymethyl-2-furfural (5-HMF) binds to the N-terminal valine of hemoglobin (HgB) and increases its affinity to O2. We used an instrumented, sedated swine model to study the effect of 5-HMF on cardiovascular parameters during exposure to acute normobaric hypoxia (NH). Methods Twenty-three sedated and instrumented swine were randomly assigned to one of three treatment groups and received equal volume of normal saline (VEH), 20 mg/kg 5-HMF (5-HMF-20) or 40 mg/kg 5-HMF (5-HMF-40). Animals then breathed 10% FiO2 for 120 min. Parameters recorded were Cardiac Output (CO), Mean Arterial Blood Pressure (MAP), Heart Rate (HR), Mean Pulmonary Artery Pressure (PAP), SaO2 and saturation of mixed venous blood (SvO2). The P50 was measured at fixed time intervals prior to and during NH. Results 5-HMF decreased P50. In the first 30 min of NH, treatment with 5-HMF-20 and 5-HMF-40 resulted in a (1) significantly smaller decrement in SaO2 and SvO2, (2) significantly lower HR and CO, and (3) smaller increase in PAP compared to VEH. In the 120 min of NH there was a trend toward improved mortality with 5-HMF treatment. Conclusion 5-HMF treatment decreased P50, improved SaO2, and mitigated increases in PAP in this swine model of NH.
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Affiliation(s)
- Richard Thomas Mahon
- Department of Undersea Medicine, Naval Medical Research Center, Silver Spring, MD, United States
| | - Geoffrey E Ciarlone
- Department of Undersea Medicine, Naval Medical Research Center, Silver Spring, MD, United States
| | - Nicholas G Roney
- Department of Undersea Medicine, Naval Medical Research Center, Silver Spring, MD, United States
| | - Joshua M Swift
- Department of Undersea Medicine, Naval Medical Research Center, Silver Spring, MD, United States
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Sotiridis A, Debevec T, McDonnell AC, Ciuha U, Eiken O, Mekjavic IB. Exercise cardiorespiratory and thermoregulatory responses in normoxic, hypoxic, and hot environment following 10-day continuous hypoxic exposure. J Appl Physiol (1985) 2018; 125:1284-1295. [DOI: 10.1152/japplphysiol.01114.2017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
We examined the effects of acclimatization to normobaric hypoxia on aerobic performance and exercise thermoregulatory responses under normoxic, hypoxic, and hot conditions. Twelve men performed tests of maximal oxygen uptake (V̇O2max) in normoxic (NOR), hypoxic [HYP; 13.5% fraction of inspired oxygen (FiO2)], and hot (HE; 35°C, 50% relative humidity) conditions in a randomized manner before and after a 10-day continuous normobaric hypoxic exposure [FiO2 = 13.65 (0.35)%, inspired partial pressure of oxygen = 87 (3) mmHg]. The acclimatization protocol included daily exercise [60 min at 50% hypoxia-specific peak power output (Wpeak)]. All maximal tests were preceded by a steady-state exercise (30 min at 40% Wpeak) to assess the sweating response. Hematological data were assessed from venous blood samples obtained before and after acclimatization. V̇o2max increased by 10.7% ( P = 0.002) and 7.9% ( P = 0.03) from pre-acclimatization to post acclimatization in NOR and HE, respectively, whereas no differences were found in HYP [pre: 39.9 (3.8) vs. post: 39.4 (5.1) ml·kg−1·min−1, P = 1.0]. However, the increase in V̇O2max did not translate into increased Wpeak in either NOR or HE. Maximal heart rate and ventilation remained unchanged following acclimatization. Νo differences were noted in the sweating gain and thresholds independent of the acclimatization or environmental conditions. Hypoxic acclimatization markedly increased hemoglobin ( P < 0.001), hematocrit ( P < 0.001), and extracellular HSP72 ( P = 0.01). These data suggest that 10 days of normobaric hypoxic acclimatization combined with moderate-intensity exercise training improves V̇o2max in NOR and HE, but does not seem to affect exercise performance or thermoregulatory responses in any of the tested environmental conditions. NEW & NOTEWORTHY The potential crossover effect of hypoxic acclimatization on performance in the heat remains unexplored. Here we show that 10-day continuous hypoxic acclimatization combined with moderate-intensity exercise training can increase maximal oxygen uptake in hot conditions.
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Affiliation(s)
- Alexandros Sotiridis
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia
- Jozef Stefan International Postgraduate School, Ljubljana, Slovenia
| | - Tadej Debevec
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia
- Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia
| | - Adam C. McDonnell
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia
| | - Urša Ciuha
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia
| | - Ola Eiken
- Department of Environmental Physiology, School of Chemistry, Biotechnology and Health, Royal Institute of Technology, Solna, Sweden
| | - Igor B. Mekjavic
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia
- Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
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Gonzalez NC, Kuwahira I. Systemic Oxygen Transport with Rest, Exercise, and Hypoxia: A Comparison of Humans, Rats, and Mice. Compr Physiol 2018; 8:1537-1573. [PMID: 30215861 DOI: 10.1002/cphy.c170051] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The objective of this article is to compare and contrast the known characteristics of the systemic O2 transport of humans, rats, and mice at rest and during exercise in normoxia and hypoxia. This analysis should help understand when rodent O2 transport findings can-and cannot-be applied to human responses to similar conditions. The O2 -transport system was analyzed as composed of four linked conductances: ventilation, alveolo-capillary diffusion, circulatory convection, and tissue capillary-cell diffusion. While the mechanisms of O2 transport are similar in the three species, the quantitative differences are naturally large. There are abundant data on total O2 consumption and on ventilatory and pulmonary diffusive conductances under resting conditions in the three species; however, there is much less available information on pulmonary gas exchange, circulatory O2 convection, and tissue O2 diffusion in mice. The scarcity of data largely derives from the difficulty of obtaining blood samples in these small animals and highlights the need for additional research in this area. In spite of the large quantitative differences in absolute and mass-specific O2 flux, available evidence indicates that resting alveolar and arterial and venous blood PO2 values under normoxia are similar in the three species. Additionally, at least in rats, alveolar and arterial blood PO2 under hypoxia and exercise remain closer to the resting values than those observed in humans. This is achieved by a greater ventilatory response, coupled with a closer value of arterial to alveolar PO2 , suggesting a greater efficacy of gas exchange in the rats. © 2018 American Physiological Society. Compr Physiol 8:1537-1573, 2018.
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Affiliation(s)
- Norberto C Gonzalez
- Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, Kansas, USA
| | - Ichiro Kuwahira
- Department of Pulmonary Medicine, Tokai University School of Medicine, Tokai University Tokyo Hospital, Tokyo, Japan
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Mourot L. Limitation of Maximal Heart Rate in Hypoxia: Mechanisms and Clinical Importance. Front Physiol 2018; 9:972. [PMID: 30083108 PMCID: PMC6064954 DOI: 10.3389/fphys.2018.00972] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2018] [Accepted: 07/02/2018] [Indexed: 12/17/2022] Open
Abstract
The use of exercise intervention in hypoxia has grown in popularity amongst patients, with encouraging results compared to similar intervention in normoxia. The prescription of exercise for patients largely rely on heart rate recordings (percentage of maximal heart rate (HRmax) or heart rate reserve). It is known that HRmax decreases with high altitude and the duration of the stay (acclimatization). At an altitude typically chosen for training (2,000-3,500 m) conflicting results have been found. Whether or not this decrease exists or not is of importance since the results of previous studies assessing hypoxic training based on HR may be biased due to improper intensity. By pooling the results of 86 studies, this literature review emphasizes that HRmax decreases progressively with increasing hypoxia. The dose–response is roughly linear and starts at a low altitude, but with large inter-study variabilities. Sex or age does not seem to be a major contributor in the HRmax decline with altitude. Rather, it seems that the greater the reduction in arterial oxygen saturation, the greater the reduction in HRmax, due to an over activity of the parasympathetic nervous system. Only a few studies reported HRmax at sea/low level and altitude with patients. Altogether, due to very different experimental design, it is difficult to draw firm conclusions in these different clinical categories of people. Hence, forthcoming studies in specific groups of patients are required to properly evaluate (1) the HRmax change during acute hypoxia and the contributing factors, and (2) the physiological and clinical effects of exercise training in hypoxia with adequate prescription of exercise training intensity if based on heart rate.
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Affiliation(s)
- Laurent Mourot
- EA 3920 Prognostic Markers and Regulatory Factors of Cardiovascular Diseases and Exercise Performance, Health, Innovation Platform, University of Franche-Comté, Besançon, France.,Tomsk Polytechnic University, Tomsk, Russia
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Abstract
Carriker, CR. Components of fatigue: mind and body. J Strength Cond Res 31(11): 3170-3176, 2017-Maximal intensity exercise requires significant energy demand. Subsequently, prolonged high-intensity effort eventually initiates volitional cessation of the event; often preceeded by a sensation of fatigue. Those examining the basis of fatigue tend to advocate either a peripheral or central model to explain such volitional failure. Practitioners and athletes who understand the tenants of fatigue can tailor their exercise regimens to target areas of potential physical or mental limitation. This review examines the rationale surrounding 2 separate models which postulate the origination of fatigue. Although the peripheral model suggests that fatigue occurs at the muscles, others have suggested a teloanticipatory cognitive component which plays a dominant role. Those familiar with both models may better integrate practice-based evidence into evidence-based practice. The highly individual nature of human performance further highlights the compulsion to comprehend the spectrum of fatigue, such that the identification of insufficiencies should mandate the development of a training purview for peak human performance.
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Affiliation(s)
- Colin R Carriker
- Department of Exercise Science, High Point University, High Point, North Carolina
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44
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Salvadego D, Keramidas ME, Kölegård R, Brocca L, Lazzer S, Mavelli I, Rittweger J, Eiken O, Mekjavic IB, Grassi B. PlanHab * : hypoxia does not worsen the impairment of skeletal muscle oxidative function induced by bed rest alone. J Physiol 2018; 596:3341-3355. [PMID: 29665013 DOI: 10.1113/jp275605] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 02/16/2018] [Indexed: 12/31/2022] Open
Abstract
KEY POINTS Superposition of hypoxia on 21 day bed rest did not worsen the impairment of skeletal muscle oxidative function induced by bed rest alone. A significant impairment of maximal oxidative performance was identified downstream of cardiovascular O2 delivery, involving both the intramuscular matching between O2 supply and utilization and mitochondrial respiration. These chronic adaptations appear to be relevant in terms of exposure to spaceflights and reduced gravity habitats (Moon or Mars), as characterized by low gravity and hypoxia, in patients with chronic diseases characterized by hypomobility/immobility and hypoxia, as well as in ageing. ABSTRACT Skeletal muscle oxidative function was evaluated in 11 healthy males (mean ± SD age 27 ± 5 years) prior to (baseline data collection, BDC) and following a 21 day horizontal bed rest (BR), carried out in normoxia ( PIO2 = 133 mmHg; N-BR) and hypoxia ( PIO2 = 90 mmHg; H-BR). H-BR was aimed at simulating reduced gravity habitats. The effects of a 21 day hypoxic ambulatory confinement ( PIO2 = 90 mmHg; H-AMB) were also assessed. Pulmonary O2 uptake ( V̇O2 ), vastus lateralis fractional O2 extraction (changes in deoxygenated haemoglobin + myoglobin concentration, Δ[deoxy(Hb + Mb)]; near-infrared spectroscopy) and femoral artery blood flow (ultrasound Doppler) were evaluated during incremental one-leg knee-extension exercise (reduced constraints to cardiovascular O2 delivery) carried out to voluntary exhaustion in a normoxic environment. Mitochondrial respiration was evaluated ex vivo by high-resolution respirometry in permeabilized vastus lateralis fibres. V̇O2peak decreased (P < 0.05) after N-BR (0.98 ± 0.13 L min-1 ) and H-BR (0.96 ± 0.17 L min-1 ) vs. BDC (1.05 ± 0.14 L min-1 ). In the presence of a decreased (by ∼6-8%) thigh muscle volume, V̇O2peak normalized per unit of muscle mass was not affected by both interventions. Δ[deoxy(Hb + Mb)]peak decreased (P < 0.05) after N-BR (65 ± 13% of limb ischaemia) and H-BR (62 ± 12%) vs. BDC (73 ± 13%). H-AMB did not alter V̇O2peak or Δ[deoxy(Hb + Mb)]peak . An overshoot of Δ[deoxy(Hb + Mb)] was evident during the first minute of unloaded exercise after N-BR and H-BR. Arterial blood flow to the lower limb during both unloaded and peak knee extension was not affected by any intervention. Maximal ADP-stimulated mitochondrial respiration decreased (P < 0.05) after all interventions vs. control. In 21 day N-BR, a significant impairment of oxidative metabolism occurred downstream of cardiovascular O2 delivery, affecting both mitochondrial respiration and presumably the intramuscular matching between O2 supply and utilization. Superposition of H on BR did not worsen the impairment induced by BR alone.
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Affiliation(s)
- Desy Salvadego
- Department of Medicine, University of Udine, Udine, Italy
| | - Michail E Keramidas
- Department of Environmental Physiology, Swedish Aerospace Physiology Centre, Royal Institute of Technology, Stockholm, Sweden
| | - Roger Kölegård
- Department of Environmental Physiology, Swedish Aerospace Physiology Centre, Royal Institute of Technology, Stockholm, Sweden
| | - Lorenza Brocca
- Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Stefano Lazzer
- Department of Medicine, University of Udine, Udine, Italy
| | - Irene Mavelli
- Department of Medicine, University of Udine, Udine, Italy
| | - Jörn Rittweger
- Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany.,Department of Pediatrics and Adolescent Medicine, Medical Faculty, University of Cologne, Cologne, Germany
| | - Ola Eiken
- Department of Environmental Physiology, Swedish Aerospace Physiology Centre, Royal Institute of Technology, Stockholm, Sweden
| | - Igor B Mekjavic
- Department of Automation, Biocybernetics and Robotics, Jožef Stefan Institute, Ljubljana, Slovenia.,Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Bruno Grassi
- Department of Medicine, University of Udine, Udine, Italy.,Institute of Bioimaging and Molecular Physiology, National Research Council, Milano, Italy
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45
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Mairbäurl H. Neocytolysis: How to Get Rid of the Extra Erythrocytes Formed by Stress Erythropoiesis Upon Descent From High Altitude. Front Physiol 2018; 9:345. [PMID: 29674976 PMCID: PMC5896414 DOI: 10.3389/fphys.2018.00345] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2017] [Accepted: 03/20/2018] [Indexed: 01/18/2023] Open
Abstract
Neocytolysis is the selective destruction of those erythrocytes that had been formed during stress-erythropoiesis in hypoxia in order to increase the oxygen transport capacity of blood. Neocytolysis likely aims at decreasing this excess amount of erythrocytes and hemoglobin (Hb) when it is not required anymore and to decrease blood viscosity. Neocytolysis seems to occur upon descent from high altitude. Similar processes seem to occur in microgravity, and are also discussed to mediate the replacement of erythrocytes containing fetal hemoglobin (HbF) with those having adult hemoglobin (HbA) after birth. This review will focus on hypoxia at high altitude. Hemoglobin concentration and total hemoglobin in blood increase by 20-50% depending on the altitude (i.e., the degree of hypoxia) and the duration of the sojourn. Upon return to normoxia hemoglobin concentration, hematocrit, and reticulocyte counts decrease faster than expected from inhibition of stress-erythropoiesis and normal erythrocyte destruction rates. In parallel, an increase in haptoglobin, bilirubin, and ferritin is observed, which serve as indirect markers of hemolysis and hemoglobin-breakdown. At the same time markers of progressing erythrocyte senescence appear even on reticulocytes. Unexpectedly, reticulocytes from hypoxic mice show decreased levels of the hypoxia-inducible factor HIF-1α and decreased activity of the BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3), which results in elevated mitochondrial activity in these cells. Furthermore, hypoxia increases the expression of miR-21, which inhibits the expression of catalase and thus decreases one of the most important mechanisms protecting against oxygen free radicals in erythrocytes. This unleashes a series of events which likely explain neocytolysis, because upon re-oxygenation systemic and mitochondrial oxygen radical formation increases and causes the selective destruction of those erythrocytes having impaired anti-oxidant capacity.
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Affiliation(s)
- Heimo Mairbäurl
- Medical Clinic VII, Sports Medicine, Translational Lung Research Center, German Center for Lung Research, University Hospital Heidelberg, Heidelberg, Germany
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46
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Chicco AJ, Le CH, Gnaiger E, Dreyer HC, Muyskens JB, D'Alessandro A, Nemkov T, Hocker AD, Prenni JE, Wolfe LM, Sindt NM, Lovering AT, Subudhi AW, Roach RC. Adaptive remodeling of skeletal muscle energy metabolism in high-altitude hypoxia: Lessons from AltitudeOmics. J Biol Chem 2018. [PMID: 29540485 DOI: 10.1074/jbc.ra117.000470] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Metabolic responses to hypoxia play important roles in cell survival strategies and disease pathogenesis in humans. However, the homeostatic adjustments that balance changes in energy supply and demand to maintain organismal function under chronic low oxygen conditions remain incompletely understood, making it difficult to distinguish adaptive from maladaptive responses in hypoxia-related pathologies. We integrated metabolomic and proteomic profiling with mitochondrial respirometry and blood gas analyses to comprehensively define the physiological responses of skeletal muscle energy metabolism to 16 days of high-altitude hypoxia (5260 m) in healthy volunteers from the AltitudeOmics project. In contrast to the view that hypoxia down-regulates aerobic metabolism, results show that mitochondria play a central role in muscle hypoxia adaptation by supporting higher resting phosphorylation potential and enhancing the efficiency of long-chain acylcarnitine oxidation. This directs increases in muscle glucose toward pentose phosphate and one-carbon metabolism pathways that support cytosolic redox balance and help mitigate the effects of increased protein and purine nucleotide catabolism in hypoxia. Muscle accumulation of free amino acids favor these adjustments by coordinating cytosolic and mitochondrial pathways to rid the cell of excess nitrogen, but might ultimately limit muscle oxidative capacity in vivo Collectively, these studies illustrate how an integration of aerobic and anaerobic metabolism is required for physiological hypoxia adaptation in skeletal muscle, and highlight protein catabolism and allosteric regulation as unexpected orchestrators of metabolic remodeling in this context. These findings have important implications for the management of hypoxia-related diseases and other conditions associated with chronic catabolic stress.
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Affiliation(s)
- Adam J Chicco
- From the Departments of Biomedical Sciences, .,Cell and Molecular Biology, and
| | | | - Erich Gnaiger
- the Medical University of Innsbruck, 6020 Innsbruck, Austria
| | - Hans C Dreyer
- the Department of Human Physiology, University of Oregon, Eugene, Oregon 97403-1240, and
| | - Jonathan B Muyskens
- the Department of Human Physiology, University of Oregon, Eugene, Oregon 97403-1240, and
| | | | - Travis Nemkov
- the Department of Biochemistry and Molecular Genetics and
| | - Austin D Hocker
- the Department of Human Physiology, University of Oregon, Eugene, Oregon 97403-1240, and
| | - Jessica E Prenni
- Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
| | - Lisa M Wolfe
- Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
| | - Nathan M Sindt
- Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado 80523
| | - Andrew T Lovering
- the Department of Human Physiology, University of Oregon, Eugene, Oregon 97403-1240, and
| | - Andrew W Subudhi
- the Department of Biology, University of Colorado, Colorado Springs, Colorado 80918
| | - Robert C Roach
- Altitude Research Center, University of Colorado-Anschutz Medical Campus, Aurora 80045, Colorado 80045
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47
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Takakura H, Ojino M, Jue T, Yamada T, Furuichi Y, Hashimoto T, Iwase S, Masuda K. Intracellular oxygen tension limits muscle contraction-induced change in muscle oxygen consumption under hypoxic conditions during Hb-free perfusion. Physiol Rep 2017; 5:5/2/e13112. [PMID: 28108649 PMCID: PMC5269414 DOI: 10.14814/phy2.13112] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Revised: 12/08/2016] [Accepted: 12/09/2016] [Indexed: 11/24/2022] Open
Abstract
Under acute hypoxic conditions, the muscle oxygen uptake (mV˙O2) during exercise is reduced by the restriction in oxygen-supplied volume to the mitochondria within the peripheral tissue. This suggests the existence of a factor restricting the mV˙O2 under hypoxic conditions at the peripheral tissue level. Therefore, this study set out to test the hypothesis that the restriction in mV˙O2 is regulated by the net decrease in intracellular oxygen tension equilibrated with myoglobin oxygen saturation (∆PmbO2) during muscle contraction under hypoxic conditions. The hindlimb of male Wistar rats (8 weeks old, n = 5) was perfused with hemoglobin-free Krebs-Henseleit buffer equilibrated with three different fractions of O2 gas: 95.0%O2, 71.3%O2, and 47.5%O2 The deoxygenated myoglobin (Mb) kinetics during muscle contraction were measured under each oxygen condition with a near-infrared spectroscopy. The ∆[deoxy-Mb] kinetics were converted to oxygen saturation of myoglobin (SmbO2), and the PmbO2 was then calculated based on the SmbO2 and the O2 dissociation curve of the Mb. The SmbO2 and PmbO2 at rest decreased with the decrease in O2 supply, and the muscle contraction caused a further decrease in SmbO2 and PmbO2 under all O2 conditions. The net increase in mV˙O2 from the muscle contraction (∆mV˙O2) gradually decreased as the ∆PmbO2 decreased during muscle contraction. The results of this study suggest that ΔPmbO2 is a key determinant of the ΔmV˙O2.
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Affiliation(s)
- Hisashi Takakura
- Faculty of Health and Sports Science, Doshisha University, Kyotanabe, Japan.,Faculty of Human Sciences, Kanazawa University, Kanazawa, Japan
| | - Minoru Ojino
- Faculty of Human Sciences, Kanazawa University, Kanazawa, Japan
| | - Thomas Jue
- Department of Biochemistry and Molecular Medicine, University of California Davis, Davis, California
| | - Tatsuya Yamada
- Faculty of Human Sciences, Kanazawa University, Kanazawa, Japan.,Department of Cell Biology, School of Medicine Johns Hopkins University, Baltimore, Maryland
| | - Yasuro Furuichi
- Faculty of Human Sciences, Kanazawa University, Kanazawa, Japan.,Department of Health Promotion Science, Tokyo Metropolitan University, Hachioji, Japan
| | - Takeshi Hashimoto
- Faculty of Sport and Health Science, Ritsumeikan University, Kusatsu, Japan
| | - Satoshi Iwase
- Department of Physiology, Aichi Medical University, Nagakute, Japan
| | - Kazumi Masuda
- Faculty of Human Sciences, Kanazawa University, Kanazawa, Japan
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48
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Why Are High-Altitude Natives So Strong at Altitude? Maximal Oxygen Transport to the Muscle Cell in Altitude Natives. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017. [PMID: 27343089 DOI: 10.1007/978-1-4899-7678-9_5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register]
Abstract
In hypoxia aerobic exercise performance of high-altitude natives is suggested to be superior to that of lowlanders; i.e., for a given altitude natives are reported to have higher maximal oxygen uptake (VO2max). The likely basis for this is a higher pulmonary diffusion capacity, which in turn ensures higher arterial O2 saturation (SaO2) and therefore also potentially a higher delivery of O2 to the exercising muscles. This review focuses on O2 transport in high-altitude Aymara. We have quantified femoral artery O2 delivery, arterial O2 extraction and calculated leg VO2 in Aymara, and compared their values with that of acclimatizing Danish lowlanders. All subjects were studied at 4100 m. At maximal exercise SaO2 dropped tremendously in the lowlanders, but did not change in the Aymara. Therefore arterial O2 content was also higher in the Aymara. At maximal exercise however, fractional O2 extraction was lower in the Aymara, and the a-vO2 difference was similar in both populations. The lower extraction levels in the Aymara were associated with lower muscle O2 conductance (a measure of muscle diffusion capacity). At any given submaximal exercise intensity, leg VO2 was always of similar magnitude in both groups, but at maximal exercise the lowlanders had higher leg blood flow, and hence also higher maximum leg VO2. With the induction of acute normoxia fractional arterial O2 extraction fell in the highlanders, but remained unchanged in the lowlanders. Hence high-altitude natives seem to be more diffusion limited at the muscle level as compared to lowlanders. In conclusion Aymara preserve very high SaO2 during hypoxic exercise (likely due to a higher lung diffusion capacity), but the effect on VO2max is reduced by a lower ability to extract O2 at the muscle level.
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49
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Siebenmann C, Robach P, Lundby C. Regulation of blood volume in lowlanders exposed to high altitude. J Appl Physiol (1985) 2017; 123:957-966. [PMID: 28572493 DOI: 10.1152/japplphysiol.00118.2017] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 05/18/2017] [Accepted: 05/31/2017] [Indexed: 12/21/2022] Open
Abstract
Humans ascending to high altitude (HA) experience a reduction in arterial oxyhemoglobin saturation and, as a result, arterial O2 content ([Formula: see text]). As HA exposure extends, this reduction in [Formula: see text] is counteracted by an increase in arterial hemoglobin concentration. Initially, hemoconcentration is exclusively related to a reduction in plasma volume (PV), whereas after several weeks a progressive expansion in total red blood cell volume (RCV) contributes, although often to a modest extent. Since the decrease in PV is more rapid and usually more pronounced than the expansion in RCV, at least during the first weeks of exposure, a reduction in circulating blood volume is common at HA. Although the regulation of hematological responses to HA has been investigated for decades, it remains incompletely understood. This is not only related to the large number of mechanisms that could be involved and the complexity of their interplay but also to the difficulty of conducting comprehensive experiments in the often secluded HA environment. In this review, we present our understanding of the kinetics, the mechanisms and the physiological relevance of the HA-induced reduction in PV and expansion in RCV.
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Affiliation(s)
- Christoph Siebenmann
- The Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark; and
| | - Paul Robach
- National School for Mountain Sports, Site of the National School for Skiing and Mountaineering (ENSA), Chamonix, France
| | - Carsten Lundby
- The Centre for Physical Activity Research, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark; and
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50
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De Smet S, van Herpt P, D'Hulst G, Van Thienen R, Van Leemputte M, Hespel P. Physiological Adaptations to Hypoxic vs. Normoxic Training during Intermittent Living High. Front Physiol 2017; 8:347. [PMID: 28620311 PMCID: PMC5449743 DOI: 10.3389/fphys.2017.00347] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Accepted: 05/11/2017] [Indexed: 12/16/2022] Open
Abstract
In the setting of “living high,” it is unclear whether high-intensity interval training (HIIT) should be performed “low” or “high” to stimulate muscular and performance adaptations. Therefore, 10 physically active males participated in a 5-week “live high-train low or high” program (TR), whilst eight subjects were not engaged in any altitude or training intervention (CON). Five days per week (~15.5 h per day), TR was exposed to normobaric hypoxia simulating progressively increasing altitude of ~2,000–3,250 m. Three times per week, TR performed HIIT, administered as unilateral knee-extension training, with one leg in normobaric hypoxia (~4,300 m; TRHYP) and with the other leg in normoxia (TRNOR). “Living high” elicited a consistent elevation in serum erythropoietin concentrations which adequately predicted the increase in hemoglobin mass (r = 0.78, P < 0.05; TR: +2.6%, P < 0.05; CON: −0.7%, P > 0.05). Muscle oxygenation during training was lower in TRHYP vs. TRNOR (P < 0.05). Muscle homogenate buffering capacity and pH-regulating protein abundance were similar between pretest and posttest. Oscillations in muscle blood volume during repeated sprints, as estimated by oscillations in NIRS-derived tHb, increased from pretest to posttest in TRHYP (~80%, P < 0.01) but not in TRNOR (~50%, P = 0.08). Muscle capillarity (~15%) as well as repeated-sprint ability (~8%) and 3-min maximal performance (~10–15%) increased similarly in both legs (P < 0.05). Maximal isometric strength increased in TRHYP (~8%, P < 0.05) but not in TRNOR (~4%, P > 0.05). In conclusion, muscular and performance adaptations were largely similar following normoxic vs. hypoxic HIIT. However, hypoxic HIIT stimulated adaptations in isometric strength and muscle perfusion during intermittent sprinting.
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Affiliation(s)
- Stefan De Smet
- Department of Kinesiology, Exercise Physiology Research Group, KU LeuvenLeuven, Belgium
| | - Paul van Herpt
- Department of Kinesiology, Exercise Physiology Research Group, KU LeuvenLeuven, Belgium
| | - Gommaar D'Hulst
- Department of Kinesiology, Exercise Physiology Research Group, KU LeuvenLeuven, Belgium
| | - Ruud Van Thienen
- Department of Kinesiology, Exercise Physiology Research Group, KU LeuvenLeuven, Belgium
| | - Marc Van Leemputte
- Department of Kinesiology, Exercise Physiology Research Group, KU LeuvenLeuven, Belgium
| | - Peter Hespel
- Department of Kinesiology, Exercise Physiology Research Group, KU LeuvenLeuven, Belgium.,Athletic Performance Center, Bakala Academy, KU LeuvenLeuven, Belgium
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