1
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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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2
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Arrebola-Moreno AL, Casuso RA, Bejder J, Bonne TC, Breenfeldt Andersen A, Aragón-Vela J, Nordsborg NB, Huertas JR. Does Hypoxia and Stress Erythropoiesis Compromise Cardiac Function in Healthy Adults? A Randomized Trial. SPORTS MEDICINE - OPEN 2022; 8:137. [PMID: 36334130 PMCID: PMC9637068 DOI: 10.1186/s40798-022-00531-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 10/20/2022] [Indexed: 11/07/2022]
Abstract
OBJECTIVES To investigate whether recombinant human erythropoietin (rHuEPO) injections during an altitude training camp impact heart function. METHODS Thirty (12 women) moderately trained subjects stayed at 2320 m altitude for 4 weeks while training. Subjects were randomized to placebo (isotonic saline) or rHuEPO (20 IU/kg body weight) i.v. injections. Transthoracic echocardiography imaging was acquired 3 days after arrival to altitude and prior to the first placebo or rHuEPO injection as well as one day after the last rHuEPO injection three weeks later. RESULTS rHuEPO did not alter cardiovascular morphology parameters, systolic or diastolic function. In the placebo group, altitude exposure improved left ventricle (LV) systolic function due to an increased twist angle but rHuEPO had no additional effects. Pulmonary arterial systolic pressure was unaffected in either group. Notably, rHuEPO hampered LV untwist rate without affecting LV early filling. CONCLUSION rHuEPO provided during mild altitude exposure does not cause any major effects on heart function. The observed alteration in LV untwist induced by rHuEPO is unlikely to have a meaningful clinical effect. Trial Registration Registered on www. CLINICALTRIALS gov (NCT04227665).
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Affiliation(s)
| | - Rafael A. Casuso
- grid.4489.10000000121678994Department of Physiology, Institute of Nutrition and Food Technology, University of Granada, Granada, Spain ,grid.449008.10000 0004 1795 4150Department of Health Sciences, Universidad Loyola Andalucía, Sevilla, Spain
| | - Jacob Bejder
- grid.5254.60000 0001 0674 042XDepartment of Nutrition, Exercise and Sports (NEXS), University of Copenhagen, Copenhagen, Denmark
| | - Thomas Christian Bonne
- grid.5254.60000 0001 0674 042XDepartment of Nutrition, Exercise and Sports (NEXS), University of Copenhagen, Copenhagen, Denmark
| | - Andreas Breenfeldt Andersen
- grid.5254.60000 0001 0674 042XDepartment of Nutrition, Exercise and Sports (NEXS), University of Copenhagen, Copenhagen, Denmark
| | - Jerónimo Aragón-Vela
- grid.4489.10000000121678994Department of Physiology, Institute of Nutrition and Food Technology, University of Granada, Granada, Spain
| | - Nikolai B. Nordsborg
- grid.5254.60000 0001 0674 042XDepartment of Nutrition, Exercise and Sports (NEXS), University of Copenhagen, Copenhagen, Denmark
| | - Jesús R. Huertas
- grid.4489.10000000121678994Department of Physiology, Institute of Nutrition and Food Technology, University of Granada, Granada, Spain
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3
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Williams AM, Levine BD, Stembridge M. A change of heart: mechanisms of cardiac adaptation to acute and chronic hypoxia. J Physiol 2022; 600:4089-4104. [PMID: 35930370 PMCID: PMC9544656 DOI: 10.1113/jp281724] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Accepted: 07/21/2022] [Indexed: 11/20/2022] Open
Abstract
Over the last 100 years, high‐altitude researchers have amassed a comprehensive understanding of the global cardiac responses to acute, prolonged and lifelong hypoxia. When lowlanders are exposed to hypoxia, the drop in arterial oxygen content demands an increase in cardiac output, which is facilitated by an elevated heart rate at the same time as ventricular volumes are maintained. As exposure is prolonged, haemoconcentration restores arterial oxygen content, whereas left ventricular filling and stroke volume are lowered as a result of a combination of reduced blood volume and hypoxic pulmonary vasoconstriction. Populations native to high‐altitude, such as the Sherpa in Asia, exhibit unique lifelong or generational adaptations to hypoxia. For example, they have smaller left ventricular volumes compared to lowlanders despite having larger total blood volume. More recent investigations have begun to explore the mechanisms underlying such adaptive responses by combining novel imaging techniques with interventions that manipulate cardiac preload, afterload, and/or contractility. This work has revealed the contributions and interactions of (i) plasma volume constriction; (ii) sympathoexcitation; and (iii) hypoxic pulmonary vasoconstriction with respect to altering cardiac loading, or otherwise preserving or enhancing biventricular systolic and diastolic function even amongst high altitude natives with excessive erythrocytosis. Despite these advances, various areas of investigation remain understudied, including potential sex‐related differences in response to high altitude. Collectively, the available evidence supports the conclusion that the human heart successfully adapts to hypoxia over the short‐ and long‐term, without signs of myocardial dysfunction in healthy humans, except in very rare cases of maladaptation.
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Affiliation(s)
- Alexandra M Williams
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, Canada.,International Collaboration on Repair Discoveries, University of British Columbia, Vancouver, BC, Canada
| | - Benjamin D Levine
- Institute for Exercise and Environmental Medicine, The University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Mike Stembridge
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, UK
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4
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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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5
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Salgado RM, Coffman KE, Bradbury KE, Mitchell KM, Yurkevicius BR, Luippold AJ, Mayer TA, Charkoudian N, Alba BK, Fulco CS, Kenefick RW. Effect of 8 days of exercise-heat acclimation on aerobic exercise performance of men in hypobaric hypoxia. Am J Physiol Regul Integr Comp Physiol 2020; 319:R114-R122. [PMID: 32432914 DOI: 10.1152/ajpregu.00048.2020] [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
Exercise-heat acclimation (EHA) induces adaptations that improve tolerance to heat exposure. Whether adaptations from EHA can also alter responses to hypobaric hypoxia (HH) conditions remains unclear. This study assessed whether EHA can alter time-trial performance and/or incidence of acute mountain sickness (AMS) during HH exposure. Thirteen sea-level (SL) resident men [SL peak oxygen consumption (V̇o2peak) 3.19 ± 0.43 L/min] completed steady-state exercise, followed by a 15-min cycle time trial and assessment of AMS before (HH1; 3,500 m) and after (HH2) an 8-day EHA protocol [120 min; 5 km/h; 2% incline; 40°C and 40% relative humidity (RH)]. EHA induced lower heart rate (HR) and core temperature and plasma volume expansion. Time-trial performance was not different between HH1 and HH2 after 2 h (106.3 ± 23.8 vs. 101.4 ± 23.0 kJ, P = 0.71) or 24 h (107.3 ± 23.4 vs. 106.3 ± 20.8 kJ, P > 0.9). From HH1 to HH2, HR and oxygen saturation, at the end of steady-state exercise and time-trial tests at 2 h and 24 h, were not different (P > 0.05). Three of 13 volunteers developed AMS during HH1 but not during HH2, whereas a fourth volunteer only developed AMS during HH2. Heat shock protein 70 was not different from HH1 to HH2 at SL [1.9 ± 0.7 vs. 1.8 ± 0.6 normalized integrated intensities (NII), P = 0.97] or after 23 h (1.8 ± 0.4 vs. 1.7 ± 0.5 NII, P = 0.78) at HH. Our results indicate that this EHA protocol had little to no effect-neither beneficial nor detrimental-on exercise performance in HH. EHA may reduce AMS in those who initially developed AMS; however, studies at higher elevations, having higher incidence rates, are needed to confirm our findings.
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Affiliation(s)
- Roy M Salgado
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Kirsten E Coffman
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts.,Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee
| | - Karleigh E Bradbury
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Katherine M Mitchell
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Beau R Yurkevicius
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts.,Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee
| | - Adam J Luippold
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Thomas A Mayer
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts.,Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee
| | - Nisha Charkoudian
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Billie K Alba
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts.,Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee
| | - Charles S Fulco
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts.,Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee
| | - Robert W Kenefick
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Natick, Massachusetts
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6
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7
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Stembridge M, Levine B. Cardiac performance with chronic hypoxia: mechanisms regulating stroke volume. CURRENT OPINION IN PHYSIOLOGY 2019. [DOI: 10.1016/j.cophys.2018.12.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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8
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Gibson OR, Taylor L, Watt PW, Maxwell NS. Cross-Adaptation: Heat and Cold Adaptation to Improve Physiological and Cellular Responses to Hypoxia. Sports Med 2018; 47:1751-1768. [PMID: 28389828 PMCID: PMC5554481 DOI: 10.1007/s40279-017-0717-z] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
To prepare for extremes of heat, cold or low partial pressures of oxygen (O2), humans can undertake a period of acclimation or acclimatization to induce environment-specific adaptations, e.g. heat acclimation (HA), cold acclimation (CA), or altitude training. While these strategies are effective, they are not always feasible due to logistical impracticalities. Cross-adaptation is a term used to describe the phenomenon whereby alternative environmental interventions, e.g. HA or CA, may be a beneficial alternative to altitude interventions, providing physiological stress and inducing adaptations observable at altitude. HA can attenuate physiological strain at rest and during moderate-intensity exercise at altitude via adaptations allied to improved O2 delivery to metabolically active tissue, likely following increases in plasma volume and reductions in body temperature. CA appears to improve physiological responses to altitude by attenuating the autonomic response to altitude. While no cross-acclimation-derived exercise performance/capacity data have been measured following CA, post-HA improvements in performance underpinned by aerobic metabolism, and therefore dependent on O2 delivery at altitude, are likely. At a cellular level, heat shock protein responses to altitude are attenuated by prior HA, suggesting that an attenuation of the cellular stress response and therefore a reduced disruption to homeostasis at altitude has occurred. This process is known as cross-tolerance. The effects of CA on markers of cross-tolerance is an area requiring further investigation. Because much of the evidence relating to cross-adaptation to altitude has examined the benefits at moderate to high altitudes, future research examining responses at lower altitudes should be conducted, given that these environments are more frequently visited by athletes and workers. Mechanistic work to identify the specific physiological and cellular pathways responsible for cross-adaptation between heat and altitude, and between cold and altitude, is warranted, as is exploration of benefits across different populations and physical activity profiles.
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Affiliation(s)
- Oliver R Gibson
- Centre for Human Performance, Exercise and Rehabilitation (CHPER), Brunel University London, Uxbridge, UK. .,Welkin Human Performance Laboratories, Centre for Sport and Exercise Science and Medicine (SESAME), University of Brighton, Denton Road, Eastbourne, UK.
| | - Lee Taylor
- Athlete Health and Performance Research Centre, ASPETAR, Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.,School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, UK
| | - Peter W Watt
- Welkin Human Performance Laboratories, Centre for Sport and Exercise Science and Medicine (SESAME), University of Brighton, Denton Road, Eastbourne, UK
| | - Neil S Maxwell
- Welkin Human Performance Laboratories, Centre for Sport and Exercise Science and Medicine (SESAME), University of Brighton, Denton Road, Eastbourne, UK
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9
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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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10
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Stembridge M, Ainslie PN, Boulet LM, Anholm J, Subedi P, Tymko MM, Willie CK, Cooper SM, Shave R. The independent effects of hypovolaemia and pulmonary vasoconstriction on ventricular function and exercise capacity during acclimatisation to 3800 m. J Physiol 2018; 597:1059-1072. [PMID: 29808473 DOI: 10.1113/jp275278] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 04/17/2018] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS We sought to determine the isolated and combined influence of hypovolaemia and hypoxic pulmonary vasoconstriction on the decrease in left ventricular (LV) function and maximal exercise capacity observed under hypobaric hypoxia. We performed echocardiography and maximal exercise tests at sea level (344 m), and following 5-10 days at the Barcroft Laboratory (3800 m; White Mountain, California) with and without (i) plasma volume expansion to sea level values and (ii) administration of the pulmonary vasodilatator sildenafil in a double-blinded and placebo-controlled trial. The high altitude-induced reduction in LV filling and ejection was abolished by plasma volume expansion but to a lesser extent by sildenafil administration; however, neither intervention had a positive effect on maximal exercise capacity. Both hypovolaemia and hypoxic pulmonary vasoconstriction play a role in the reduction of LV filling at 3800 m, but the increase in LV filling does not influence exercise capacity at this moderate altitude. ABSTRACT We aimed to determine the isolated and combined contribution of hypovolaemia and hypoxic pulmonary vasoconstriction in limiting left ventricular (LV) function and exercise capacity under chronic hypoxaemia at high altitude. In a double-blinded, randomised and placebo-controlled design, 12 healthy participants underwent echocardiography at rest and during submaximal exercise before completing a maximal test to exhaustion at sea level (SL; 344 m) and after 5-10 days at 3800 m. Plasma volume was normalised to SL values, and hypoxic pulmonary vasoconstriction was reversed by administration of sildenafil (50 mg) to create four unique experimental conditions that were compared with SL values: high altitude (HA), Plasma Volume Expansion (HA-PVX), Sildenafil (HA-SIL) and Plasma Volume Expansion with Sildenafil (HA-PVX-SIL). High altitude exposure reduced plasma volume by 11% (P < 0.01) and increased pulmonary artery systolic pressure (19.6 ± 4.3 vs. 26.0 ± 5.4, P < 0.001); these differences were abolished by PVX and SIL respectively. LV end-diastolic volume (EDV) and stroke volume (SV) were decreased upon ascent to high altitude, but were comparable to sea level in the HA-PVX trial. LV EDV and SV were also elevated in the HA-SIL and HA-PVX-SIL trials compared to HA, but to a lesser extent. Neither PVX nor SIL had a significant effect on the LV EDV and SV response to exercise, or the maximal oxygen consumption or peak power output. In summary, at 3800 m both hypovolaemia and hypoxic pulmonary vasoconstriction contribute to the decrease in LV filling, but restoring LV filling does not confer an improvement in maximal exercise performance.
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Affiliation(s)
- Mike Stembridge
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Philip N Ainslie
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Lindsey M Boulet
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - James Anholm
- VA Loma Linda Healthcare System and Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Prajan Subedi
- VA Loma Linda Healthcare System and Loma Linda University School of Medicine, Loma Linda, CA, USA
| | - Michael M Tymko
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Christopher K Willie
- Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
| | - Stephen-Mark Cooper
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK
| | - Rob Shave
- Cardiff Centre for Exercise and Health, Cardiff Metropolitan University, Cardiff, UK.,Centre for Heart Lung and Vascular Health, University of British Columbia, Kelowna, BC, Canada
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11
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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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12
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Keramidas ME, Mekjavic IB, Eiken O. LunHab: interactive effects of a 10 day sustained exposure to hypoxia and bedrest on aerobic exercise capacity in male lowlanders. Exp Physiol 2017; 102:694-710. [DOI: 10.1113/ep086167] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 03/20/2017] [Indexed: 11/08/2022]
Affiliation(s)
- Michail E. Keramidas
- Department of Environmental Physiology; Swedish Aerospace Physiology Center; School of Technology and Health; Royal Institute of Technology; Stockholm 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 BC Canada
| | - Ola Eiken
- Department of Environmental Physiology; Swedish Aerospace Physiology Center; School of Technology and Health; Royal Institute of Technology; Stockholm Sweden
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13
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Ainslie PN. Professor Bengt Saltin Symposium - Environmental challenges to human performance. Appl Physiol Nutr Metab 2016; 42:104-107. [PMID: 28006436 DOI: 10.1139/apnm-2016-0319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This short review is from a presentation made at the Bengt Saltin Symposium, October 15-17, at the 2015 Canadian Society for Exercise Physiology conference, Hamilton, Canada. The review provides context of the important work of the late Dr. Saltin's contributions to environmental physiology. In addition to well-controlled laboratory experiments to better understand the influence of hypoxia or temperature, or both, Dr. Saltin also led several field expeditions to the North Greenland, Kenya, Himalayas, and the Andes, where he studied several aspects of human adaptation to environment. The 1998 Danish High-Altitude Expedition to the Andes, in particular, resulted in many major contributions to the field of altitude physiology including, but not limited to, mechanisms of reductions in maximal oxygen uptake, the lactate paradox, acclimatization, muscle metabolism, gas exchange, cerebrovascular physiology, etc. Of note, many of these related studies were conducted in both Danish sojourners to altitude and Bolivian altitude natives of Aymara ancestry, thus providing some of the most mechanistic comparisons with high altitude natives to date. A framework of these physiological contributions in terrestrial extremes is provided in this review.
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Affiliation(s)
- Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia - Okanagan Campus, 3333 University Way, Kelowna, BC V1V 1V7, Canada.,Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, Faculty of Health and Social Development, University of British Columbia - Okanagan Campus, 3333 University Way, Kelowna, BC V1V 1V7, Canada
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14
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Keramidas ME, Kölegård R, Mekjavic IB, Eiken O. PlanHab: hypoxia exaggerates the bed-rest-induced reduction in peak oxygen uptake during upright cycle ergometry. Am J Physiol Heart Circ Physiol 2016; 311:H453-64. [PMID: 27342877 DOI: 10.1152/ajpheart.00304.2016] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Accepted: 06/20/2016] [Indexed: 11/22/2022]
Abstract
The study examined the effects of hypoxia and horizontal bed rest, separately and in combination, on peak oxygen uptake (V̇o2 peak) during upright cycle ergometry. Ten male lowlanders underwent three 21-day confinement periods in a counterbalanced order: 1) normoxic bed rest [NBR; partial pressure of inspired O2 (PiO2 ) = 133.1 ± 0.3 mmHg]; 2) hypoxic bed rest (HBR; PiO2 = 90.0 ± 0.4 mmHg), and 3) hypoxic ambulation (HAMB; PiO2 = 90.0 ± 0.4 mmHg). Before and after each confinement, subjects performed two incremental-load trials to exhaustion, while inspiring either room air (AIR), or a hypoxic gas (HYPO; PiO2 = 90.0 ± 0.4 mmHg). Changes in regional oxygenation of the vastus lateralis muscle and the frontal cerebral cortex were monitored with near-infrared spectroscopy. Cardiac output (CO) was recorded using a bioimpedance method. The AIR V̇o2 peak was decreased by both HBR (∼13.5%; P ≤ 0.001) and NBR (∼8.6%; P ≤ 0.001), with greater drop after HBR (P = 0.01). The HYPO V̇o2 peak was also reduced by HBR (-9.7%; P ≤ 0.001) and NBR (-6.1%; P ≤ 0.001). Peak CO was lower after both bed-rest interventions, and especially after HBR (HBR: ∼13%, NBR: ∼7%; P ≤ 0.05). Exercise-induced alterations in muscle and cerebral oxygenation were blunted in a similar manner after both bed-rest confinements. No changes were observed in HAMB. Hence, the bed-rest-induced decrease in V̇o2 peak was exaggerated by hypoxia, most likely due to a reduction in convective O2 transport, as indicated by the lower peak values of CO.
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Affiliation(s)
- Michail E Keramidas
- Department of Environmental Physiology, Swedish Aerospace Physiology Center, School of Technology and Health, Royal Institute of Technology, Stockholm, Sweden;
| | - Roger Kölegård
- Department of Environmental Physiology, Swedish Aerospace Physiology Center, School of Technology and Health, Royal Institute of Technology, Stockholm, Sweden
| | - Igor B Mekjavic
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia; and Department of Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Ola Eiken
- Department of Environmental Physiology, Swedish Aerospace Physiology Center, School of Technology and Health, Royal Institute of Technology, Stockholm, Sweden
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15
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Siebenmann C, Lundby C. Regulation of cardiac output in hypoxia. Scand J Med Sci Sports 2015; 25 Suppl 4:53-9. [DOI: 10.1111/sms.12619] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/14/2015] [Indexed: 10/22/2022]
Affiliation(s)
- Christoph Siebenmann
- Department of Environmental Physiology; School of Technology and Health; Royal Institute of Technology; Solna Sweden
| | - Carsten Lundby
- Center for Integrative Human Physiology; Institute of Physiology; University of Zürich; Zürich Switzerland
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16
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Stembridge M, Ainslie PN, Shave R. Mechanisms underlying reductions in stroke volume at rest and during exercise at high altitude. Eur J Sport Sci 2015; 16:577-84. [DOI: 10.1080/17461391.2015.1071876] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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17
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White AC, Salgado RM, Astorino TA, Loeppky JA, Schneider SM, McCormick JJ, McLain TA, Kravitz L, Mermier CM. The effect of 10 days of heat acclimation on exercise performance in acute hypobaric hypoxia (4350 m). Temperature (Austin) 2015; 3:176-85. [PMID: 27227084 PMCID: PMC4861181 DOI: 10.1080/23328940.2015.1072659] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 07/08/2015] [Indexed: 01/09/2023] Open
Abstract
To examine the effect (“cross-tolerance”) of heat acclimation (HA) on exercise performance upon exposure to acute hypobaric hypoxia (4350 m). Eight male cyclists residing at 1600 m performed tests of maximal aerobic capacity (VO2max) at 1600 m and 4350 m, a 16 km time-trial at 4350 m, and a heat tolerance test at 1600 m before and after 10 d HA at 40°C, 20% RH. Resting blood samples were obtained pre-and post- HA to estimate changes in plasma volume (ΔPV). Successful HA was indicated by significantly lower exercise heart rate and rectal temperature on day 10 vs. day 1 of HA and during the heat tolerance tests. Heat acclimation caused a 1.9% ΔPV, however VO2max was not significantly different at 1600 m or 4350 m. Time-trial cycling performance improved 28 sec after HA (p = 0.07), suggesting a possible benefit for exercise performance at acute altitude and that cross-tolerance between these variables may exist in humans. These findings do not clearly support the use of HA to improve exercise capacity and performance upon acute hypobaric hypoxia, however they do indicate that HA is not detrimental to either exercise capacity or performance.
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Affiliation(s)
- Ailish C White
- Department of Kinesiology, Point Loma Nazarene University, San Diego, CA, USA; Department of Health, Exercise, and Sports Sciences, University of New Mexico, Albuquerque, NM, USA
| | - Roy M Salgado
- Department of Health, Exercise, and Sports Sciences, University of New Mexico, Albuquerque, NM, USA; Department of Kinesiology, Occidental College, Los Angeles, CA, USA
| | - Todd A Astorino
- Department of Kinesiology, California State University San Marcos , San Marcos, CA, USA
| | - Jack A Loeppky
- Department of Health, Exercise, and Sports Sciences, University of New Mexico , Albuquerque, NM, USA
| | - Suzanne M Schneider
- Department of Health, Exercise, and Sports Sciences, University of New Mexico , Albuquerque, NM, USA
| | - James J McCormick
- Department of Health, Exercise, and Sports Sciences, University of New Mexico , Albuquerque, NM, USA
| | - Trisha A McLain
- Department of Health, Exercise, and Sports Sciences, University of New Mexico , Albuquerque, NM, USA
| | - Len Kravitz
- Department of Health, Exercise, and Sports Sciences, University of New Mexico , Albuquerque, NM, USA
| | - Christine M Mermier
- Department of Health, Exercise, and Sports Sciences, University of New Mexico , Albuquerque, NM, USA
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18
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Stembridge M, Ainslie PN, Hughes MG, Stöhr EJ, Cotter JD, Tymko MM, Day TA, Bakker A, Shave R. Impaired myocardial function does not explain reduced left ventricular filling and stroke volume at rest or during exercise at high altitude. J Appl Physiol (1985) 2015; 119:1219-27. [PMID: 25749445 DOI: 10.1152/japplphysiol.00995.2014] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2014] [Accepted: 03/02/2015] [Indexed: 02/07/2023] Open
Abstract
Impaired myocardial systolic contraction and diastolic relaxation have been suggested as possible mechanisms contributing to the decreased stroke volume (SV) observed at high altitude (HA). To determine whether intrinsic myocardial performance is a limiting factor in the generation of SV at HA, we assessed left ventricular (LV) systolic and diastolic mechanics and volumes in 10 healthy participants (aged 32 ± 7; mean ± SD) at rest and during exercise at sea level (SL; 344 m) and after 10 days at 5,050 m. In contrast to SL, LV end-diastolic volume was ∼19% lower at rest (P = 0.004) and did not increase during exercise despite a greater untwisting velocity. Furthermore, resting SV was lower at HA (∼17%; 60 ± 10 vs. 70 ± 8 ml) despite higher LV twist (43%), apical rotation (115%), and circumferential strain (17%). With exercise at HA, the increase in SV was limited (12 vs. 22 ml at SL), and LV apical rotation failed to augment. For the first time, we have demonstrated that EDV does not increase upon exercise at high altitude despite enhanced in vivo diastolic relaxation. The increase in LV mechanics at rest may represent a mechanism by which SV is defended in the presence of a reduced EDV. However, likely because of the higher LV mechanics at rest, no further increase was observed up to 50% peak power. Consequently, although hypoxia does not suppress systolic function per se, the capacity to increase SV through greater deformation during submaximal exercise at HA is restricted.
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Affiliation(s)
- Mike Stembridge
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom;
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan Campus, Kelowna, Canada
| | - Michael G Hughes
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Eric J Stöhr
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - James D Cotter
- School of Sport and Exercise Sciences, University of Otago, Dunedin, New Zealand
| | - Michael M Tymko
- Centre for Heart, Lung and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan Campus, Kelowna, Canada; Department of Biology, Mount Royal University, Calgary, Canada; and
| | - Trevor A Day
- Department of Biology, Mount Royal University, Calgary, Canada; and
| | - Akke Bakker
- MIRA Institute, University of Twente, Twente, The Netherlands
| | - Rob Shave
- Cardiff School of Sport, Cardiff Metropolitan University, Cardiff, United Kingdom
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19
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Elliott JE, Laurie SS, Kern JP, Beasley KM, Goodman RD, Kayser B, Subudhi AW, Roach RC, Lovering AT. AltitudeOmics: impaired pulmonary gas exchange efficiency and blunted ventilatory acclimatization in humans with patent foramen ovale after 16 days at 5,260 m. J Appl Physiol (1985) 2015; 118:1100-12. [PMID: 25678698 DOI: 10.1152/japplphysiol.00879.2014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 02/08/2015] [Indexed: 12/29/2022] Open
Abstract
A patent foramen ovale (PFO), present in ∼40% of the general population, is a potential source of right-to-left shunt that can impair pulmonary gas exchange efficiency [i.e., increase the alveolar-to-arterial Po2 difference (A-aDO2)]. Prior studies investigating human acclimatization to high-altitude with A-aDO2 as a key parameter have not investigated differences between subjects with (PFO+) or without a PFO (PFO-). We hypothesized that in PFO+ subjects A-aDO2 would not improve (i.e., decrease) after acclimatization to high altitude compared with PFO- subjects. Twenty-one (11 PFO+) healthy sea-level residents were studied at rest and during cycle ergometer exercise at the highest iso-workload achieved at sea level (SL), after acute transport to 5,260 m (ALT1), and again at 5,260 m after 16 days of high-altitude acclimatization (ALT16). In contrast to PFO- subjects, PFO+ subjects had 1) no improvement in A-aDO2 at rest and during exercise at ALT16 compared with ALT1, 2) no significant increase in resting alveolar ventilation, or alveolar Po2, at ALT16 compared with ALT1, and consequently had 3) an increased arterial Pco2 and decreased arterial Po2 and arterial O2 saturation at rest at ALT16. Furthermore, PFO+ subjects had an increased incidence of acute mountain sickness (AMS) at ALT1 concomitant with significantly lower peripheral O2 saturation (SpO2). These data suggest that PFO+ subjects have increased susceptibility to AMS when not taking prophylactic treatments, that right-to-left shunt through a PFO impairs pulmonary gas exchange efficiency even after acclimatization to high altitude, and that PFO+ subjects have blunted ventilatory acclimatization after 16 days at altitude compared with PFO- subjects.
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Affiliation(s)
| | - Steven S Laurie
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - Julia P Kern
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - Kara M Beasley
- Department of Human Physiology, University of Oregon, Eugene, Oregon
| | - Randall D Goodman
- Oregon Heart and Vascular Institute, Echocardiography, Springfield, Oregon
| | - Bengt Kayser
- University of Lausanne, Department of Physiology and Institute of Sports Sciences, Lausanne, Switzerland
| | - Andrew W Subudhi
- Altitude Research Center, University of Colorado Anschutz Medical Campus, Denver, Colorado; and Department of Biology, University of Colorado, Colorado Springs, Colorado
| | - Robert C Roach
- Altitude Research Center, University of Colorado Anschutz Medical Campus, Denver, Colorado; and
| | - Andrew T Lovering
- Department of Human Physiology, University of Oregon, Eugene, Oregon;
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20
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Figueroa RA, Arnold AC, Nwazue VC, Okamoto LE, Paranjape SY, Black BK, Diedrich A, Robertson D, Biaggioni I, Raj SR, Gamboa A. Acute volume loading and exercise capacity in postural tachycardia syndrome. J Appl Physiol (1985) 2014; 117:663-8. [PMID: 25059240 DOI: 10.1152/japplphysiol.00367.2014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Postural tachycardia syndrome (POTS) is associated with exercise intolerance, hypovolemia, and cardiac atrophy, which may contribute to reduced stroke volume and compensatory exaggerated heart rate (HR) increases. Acute volume loading with intravenous (iv) saline reduces HR and improves orthostatic tolerance and symptoms in POTS, but its effect on exercise capacity is unknown. In this study, we determined the effect of iv saline infusion on peak exercise capacity (VO2peak) in POTS. Nineteen patients with POTS participated in a sequential study. VO2peak was measured on two separate study days, following administration of placebo or 1 liter of i.v. saline (NaCl 0.9%). Patients exercised on a semirecumbent bicycle with resistance increased by 25 W every 2 min until maximal effort was achieved. Patients exhibited blood volume deficits (-13.4 ± 1.4% ideal volume), consistent with mild to moderate hypovolemia. At baseline, saline significantly increased stroke volume (saline 80 ± 8 ml vs. placebo 64 ± 4 ml; P = 0.010), increased cardiac output (saline 6.9 ± 0.5 liter/min vs. placebo 5.7 ± 0.2 liter/min; P = 0.021), and reduced systemic vascular resistance (saline 992.6 ± 70.0 dyn-s/cm(5) vs. placebo 1,184.0 ± 50.8 dyn-s/cm(5); P = 0.011), with no effect on HR or blood pressure. During exercise, saline did not produce differences in VO2peak (saline 26.3 ± 1.2 mg·kg(-1)·min(-1) vs. placebo 27.7 ± 1.8 mg·kg(-1)·min(-1); P = 0.615), peak HR [saline 174 ± 4 beats per minute (bpm) vs. placebo 175 ± 3 bpm; P = 0.672] or other cardiovascular parameters. These findings suggest that acute volume loading with saline does not improve VO2peak or cardiovascular responses to exercise in POTS, despite improvements in resting hemodynamic function.
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Affiliation(s)
- Rocío A Figueroa
- Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University, Nashville, Tennessee; and
| | - Amy C Arnold
- Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University, Nashville, Tennessee; and
| | - Victor C Nwazue
- Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University, Nashville, Tennessee; and
| | - Luis E Okamoto
- Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University, Nashville, Tennessee; and
| | - Sachin Y Paranjape
- Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University, Nashville, Tennessee; and
| | - Bonnie K Black
- Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University, Nashville, Tennessee; and
| | - Andre Diedrich
- Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University, Nashville, Tennessee; and
| | - David Robertson
- Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University, Nashville, Tennessee; and Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Pharmacology, Vanderbilt University, Nashville, Tennessee
| | - Italo Biaggioni
- Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University, Nashville, Tennessee; and Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Pharmacology, Vanderbilt University, Nashville, Tennessee
| | - Satish R Raj
- Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University, Nashville, Tennessee; and Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Pharmacology, Vanderbilt University, Nashville, Tennessee
| | - Alfredo Gamboa
- Autonomic Dysfunction Center, Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University, Nashville, Tennessee; and
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21
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Subudhi AW, Bourdillon N, Bucher J, Davis C, Elliott JE, Eutermoster M, Evero O, Fan JL, Houten SJV, Julian CG, Kark J, Kark S, Kayser B, Kern JP, Kim SE, Lathan C, Laurie SS, Lovering AT, Paterson R, Polaner DM, Ryan BJ, Spira JL, Tsao JW, Wachsmuth NB, Roach RC. AltitudeOmics: the integrative physiology of human acclimatization to hypobaric hypoxia and its retention upon reascent. PLoS One 2014; 9:e92191. [PMID: 24658407 PMCID: PMC3962396 DOI: 10.1371/journal.pone.0092191] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2013] [Accepted: 02/19/2014] [Indexed: 11/19/2022] Open
Abstract
An understanding of human responses to hypoxia is important for the health of millions of people worldwide who visit, live, or work in the hypoxic environment encountered at high altitudes. In spite of dozens of studies over the last 100 years, the basic mechanisms controlling acclimatization to hypoxia remain largely unknown. The AltitudeOmics project aimed to bridge this gap. Our goals were 1) to describe a phenotype for successful acclimatization and assess its retention and 2) use these findings as a foundation for companion mechanistic studies. Our approach was to characterize acclimatization by measuring changes in arterial oxygenation and hemoglobin concentration [Hb], acute mountain sickness (AMS), cognitive function, and exercise performance in 21 subjects as they acclimatized to 5260 m over 16 days. We then focused on the retention of acclimatization by having subjects reascend to 5260 m after either 7 (n = 14) or 21 (n = 7) days at 1525 m. At 16 days at 5260 m we observed: 1) increases in arterial oxygenation and [Hb] (compared to acute hypoxia: PaO2 rose 9±4 mmHg to 45±4 while PaCO2 dropped a further 6±3 mmHg to 21±3, and [Hb] rose 1.8±0.7 g/dL to 16±2 g/dL; 2) no AMS; 3) improved cognitive function; and 4) improved exercise performance by 8±8% (all changes p<0.01). Upon reascent, we observed retention of arterial oxygenation but not [Hb], protection from AMS, retention of exercise performance, less retention of cognitive function; and noted that some of these effects lasted for 21 days. Taken together, these findings reveal new information about retention of acclimatization, and can be used as a physiological foundation to explore the molecular mechanisms of acclimatization and its retention.
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Affiliation(s)
- Andrew W. Subudhi
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
- Department of Biology, University of Colorado Colorado Springs, Colorado Springs, Colorado, United States of America
| | - Nicolas Bourdillon
- Institute of Sports Sciences and Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Jenna Bucher
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States of America
| | - Christopher Davis
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Jonathan E. Elliott
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States of America
| | - Morgan Eutermoster
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Oghenero Evero
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Jui-Lin Fan
- Institute of Sports Sciences and Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
- Lemanic Doctoral School of Neuroscience, University of Lausanne, Lausanne, Switzerland
| | - Sonja Jameson-Van Houten
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Colleen G. Julian
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Jonathan Kark
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Sherri Kark
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - Bengt Kayser
- Institute of Sports Sciences and Department of Physiology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Julia P. Kern
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States of America
| | - See Eun Kim
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States of America
| | - Corinna Lathan
- AnthroTronix, Inc., Silver Spring, Maryland, United States of America
| | - Steven S. Laurie
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States of America
| | - Andrew T. Lovering
- Department of Human Physiology, University of Oregon, Eugene, Oregon, United States of America
| | - Ryan Paterson
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
| | - David M. Polaner
- Departments of Anesthesiology and Pediatrics, University of Colorado School of Medicine and Children's Hospital Colorado, Aurora, Colorado, United States of America
| | - Benjamin J. Ryan
- Department of Integrative Physiology, University of Colorado Boulder, Boulder, Colorado, United States of America
| | - James L. Spira
- United States Department of Veterans Affairs, National Center for PTSD, Pacific Islands Health Care System, and Department of Psychiatry, University of Hawaii John A. Burns School of Medicine, Honolulu, Hawaii, United States of America
| | - Jack W. Tsao
- Wounded, Ill & Injured Directorate (M9), United States Navy Bureau of Medicine and Surgery, Falls Church, Virginia, United States of America
| | - Nadine B. Wachsmuth
- Department of Sports Medicine/Sports Physiology, University of Bayreuth, Bayreuth, Germany
| | - Robert C. Roach
- Altitude Research Center, Department of Emergency Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, United States of America
- * E-mail:
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22
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Elliott AD, Skowno J, Prabhu M, Noakes TD, Ansley L. Evidence of cardiac functional reserve upon exhaustion during incremental exercise to determine VO2max. Br J Sports Med 2013; 49:128-32. [PMID: 23293009 DOI: 10.1136/bjsports-2012-091752] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
BACKGROUND There remains considerable debate regarding the limiting factor(s) for maximal oxygen uptake (VO2max). Previous studies have shown that the central circulation may be the primary limiting factor for VO2max and that cardiac work increases beyond VO2max. AIM We sought to evaluate whether the work of the heart limits VO2max during upright incremental cycle exercise to exhaustion. METHODS Eight trained men completed two incremental exercise trials, each terminating with exercise at two different rates of work eliciting VO2max (MAX and SUPRAMAX). During each exercise trial we continuously recorded cardiac output using pulse-contour analysis calibrated with a lithium dilution method. Intra-arterial pressure was recorded from the radial artery while pulmonary gas exchange was measured continuously for an assessment of oxygen uptake. RESULTS The workload during SUPRAMAX (mean±SD: 346.5±43.2 W) was 10% greater than that achieved during MAX (315±39.3 W). There was no significant difference between MAX and SUPRAMAX for Q (28.7 vs 29.4 L/min) or VO2 (4.3 vs 4.3 L/min). Mean arterial pressure was significantly higher during SUPRAMAX, corresponding to a higher cardiac power output (8.1 vs 8.5 W; p<0.06). CONCLUSIONS Despite similar VO2 and Q, the greater cardiac work during SUPRAMAX supports the view that the heart is working submaximally at exhaustion during an incremental exercise test (MAX).
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Affiliation(s)
- Adrian D Elliott
- School of Life Sciences, Kingston University, Surrey, UK Discipline of Physiology, University of Adelaide, Adelaide, Australia
| | - Justin Skowno
- The Children's Hospital at Westmead, Sydney, Australiai Discipline of Paediatrics and Child Health, The University of Sydney, Sydney, Australia
| | | | - Timothy David Noakes
- UCT/MRC Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, University of Cape Town, Newlands, South Africa
| | - Les Ansley
- School of Psychology and Sports Sciences, Northumbria University, Newcastle Upon Tyne, UK
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23
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Jacobs RA, Lundby C, Robach P, Gassmann M. Red blood cell volume and the capacity for exercise at moderate to high altitude. Sports Med 2012; 42:643-63. [PMID: 22741918 DOI: 10.1007/bf03262286] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Hypoxia-stimulated erythropoiesis, such as that observed when red blood cell volume (RCV) increases in response to high-altitude exposure, is well understood while the physiological importance is not. Maximal exercise tests are often performed in hypoxic conditions following some form of RCV manipulation in an attempt to elucidate oxygen transport limitations at moderate to high altitudes. Such attempts, however, have not made clear the extent to which RCV is of benefit to exercise at such elevations. Changes in RCV at sea level clearly have a direct influence on maximal exercise capacity. Nonetheless, at elevations above 3000 m, the evidence is not that clear. Certain studies demonstrate either a direct benefit or decrement to exercise capacity in response to an increase or decrease, respectively, in RCV whereas other studies report negligible effects of RCV manipulation on exercise capacity. Adding to the uncertainty regarding the importance of RCV at high altitude is the observation that Andean and Tibetan high-altitude natives exhibit similar exercise capacities at high altitude (3900 m) even though Andean natives often present with a higher percent haematocrit (Hct) when compared with both lowland natives and Tibetans. The current review summarizes past literature that has examined the effect of RCV changes on maximal exercise capacity at moderate to high altitudes, and discusses the explanation elucidating these seemingly paradoxical observations.
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Affiliation(s)
- Robert A Jacobs
- Institute of Veterinary Physiology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
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24
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Calbet JAL, Lundby C. Skeletal muscle vasodilatation during maximal exercise in health and disease. J Physiol 2012; 590:6285-96. [PMID: 23027820 DOI: 10.1113/jphysiol.2012.241190] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Maximal exercise vasodilatation results from the balance between vasoconstricting and vasodilating signals combined with the vascular reactivity to these signals. During maximal exercise with a small muscle mass the skeletal muscle vascular bed is fully vasodilated. During maximal whole body exercise, however, vasodilatation is restrained by the sympathetic system. This is necessary to avoid hypotension since the maximal vascular conductance of the musculature exceeds the maximal pumping capacity of the heart. Endurance training and high-intensity intermittent knee extension training increase the capacity for maximal exercise vasodilatation by 20-30%, mainly due to an enhanced vasodilatory capacity, as maximal exercise perfusion pressure changes little with training. The increase in maximal exercise vascular conductance is to a large extent explained by skeletal muscle hypertrophy and vascular remodelling. The vasodilatory capacity during maximal exercise is reduced or blunted with ageing, as well as in chronic heart failure patients and chronically hypoxic humans; reduced vasodilatory responsiveness and increased sympathetic activity (and probably, altered sympatholysis) are potential mechanisms accounting for this effect. Pharmacological counteraction of the sympathetic restraint may result in lower perfusion pressure and reduced oxygen extraction by the exercising muscles. However, at the same time fast inhibition of the chemoreflex in maximally exercising humans may result in increased vasodilatation, further confirming a restraining role of the sympathetic nervous system on exercise-induced vasodilatation. This is likely to be critical for the maintenance of blood pressure in exercising patients with a limited heart pump capacity.
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Affiliation(s)
- Jose A L Calbet
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira, Las Palmas de Gran Canaria, 35017, Spain.
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Jacobs RA, Lundby C, Robach P, Gassmann M. Red Blood Cell Volume and the Capacity for Exercise at Moderate to High Altitude. Sports Med 2012. [DOI: 10.2165/11632440-000000000-00000] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Abstract
Altitude exposure is associated with major changes in cardiovascular function. The initial cardiovascular response to altitude is characterized by an increase in cardiac output with tachycardia, no change in stroke volume, whereas blood pressure may temporarily be slightly increased. After a few days of acclimatization, cardiac output returns to normal, but heart rate remains increased, so that stroke volume is decreased. Pulmonary artery pressure increases without change in pulmonary artery wedge pressure. This pattern is essentially unchanged with prolonged or lifelong altitude sojourns. Ventricular function is maintained, with initially increased, then preserved or slightly depressed indices of systolic function, and an altered diastolic filling pattern. Filling pressures of the heart remain unchanged. Exercise in acute as well as in chronic high-altitude exposure is associated with a brisk increase in pulmonary artery pressure. The relationships between workload, cardiac output, and oxygen uptake are preserved in all circumstances, but there is a decrease in maximal oxygen consumption, which is accompanied by a decrease in maximal cardiac output. The decrease in maximal cardiac output is minimal in acute hypoxia but becomes more pronounced with acclimatization. This is not explained by hypovolemia, acid-bases status, increased viscosity on polycythemia, autonomic nervous system changes, or depressed systolic function. Maximal oxygen uptake at high altitudes has been modeled to be determined by the matching of convective and diffusional oxygen transport systems at a lower maximal cardiac output. However, there has been recent suggestion that 10% to 25% of the loss in aerobic exercise capacity at high altitudes can be restored by specific pulmonary vasodilating interventions. Whether this is explained by an improved maximum flow output by an unloaded right ventricle remains to be confirmed. Altitude exposure carries no identified risk of myocardial ischemia in healthy subjects but has to be considered as a potential stress in patients with previous cardiovascular conditions.
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Martin DS, Levett DZH, Grocott MPW, Montgomery HE. Variation in human performance in the hypoxic mountain environment. Exp Physiol 2010; 95:463-70. [DOI: 10.1113/expphysiol.2009.047589] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Calbet JAL, Robach P, Lundby C. The exercising heart at altitude. Cell Mol Life Sci 2009; 66:3601-13. [PMID: 19809792 PMCID: PMC11115914 DOI: 10.1007/s00018-009-0148-6] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Accepted: 08/20/2009] [Indexed: 10/20/2022]
Abstract
Maximal cardiac output is reduced in severe acute hypoxia but also in chronic hypoxia by mechanisms that remain poorly understood. In theory, the reduction of maximal cardiac output could result from: (1) a regulatory response from the central nervous system, (2) reduction of maximal pumping capacity of the heart due to insufficient coronary oxygen delivery prior to the achievement of the normoxic maximal cardiac output, or (3) reduced central command. In this review, we focus on the effects that acute and chronic hypoxia have on the pumping capacity of the heart, particularly on myocardial contractility and the molecular responses elicited by acute and chronic hypoxia in the cardiac myocytes. Special emphasis is put on the cardioprotective effects of chronic hypoxia.
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Affiliation(s)
- José A L Calbet
- Department of Physical Education, University of Las Palmas de Gran Canaria, Campus Universitario de Tafira, 35017, Las Palmas de Gran Canaria, Canary Islands, Spain.
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Abstract
Aerobic exercise capacity decreases with exposure to hypoxia. This article focuses on the effects of hypoxia on nervous system function and the potential consequences for the exercising human. Emphasis is put on somatosensory muscle afferents due to their crucial role in the reflex inhibition of muscle activation and in cardiorespiratory reflex control during exercise. We review the evidence of hypoxia influences on muscle afferents and discuss important consequences for exercise performance. Efferent (motor) nerves are less affected at altitude and are thought to stay fairly functional even in severe levels of arterial hypoxemia. Altitude also alters autonomic nervous system functions, which are thought to play an important role in the regulation of cardiac output and ventilation. Finally, the consequences of hypoxia-induced cortical adaptations and dysfunctions are evaluated in terms of neurotransmitter turnover, brain electrical activity, and cortical excitability. Even though the cessation of exercise or the reduction of exercise intensity, when reaching maximum performance, implies reduced motor recruitment by the nervous system, the mechanisms that lead to the de-recruitment of active muscle are still not well understood. In moderate hypoxia, muscle afferents appear to play an important role, whereas in severe hypoxia brain oxygenation may play a more important role.
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Affiliation(s)
- Markus Amann
- University of Zürich , Institute of Physiology, and ETH Zürich, Exercise Physiology, Zürich, Switzerland.
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Calbet JAL, Rådegran G, Boushel R, Saltin B. On the mechanisms that limit oxygen uptake during exercise in acute and chronic hypoxia: role of muscle mass. J Physiol 2008; 587:477-90. [PMID: 19047206 DOI: 10.1113/jphysiol.2008.162271] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Peak aerobic power in humans (VO2,peak) is markedly affected by inspired O2 tension (FIO2). The question to be answered in this study is what factor plays a major role in the limitation of muscle peak VO2 in hypoxia: arterial O2 partial pressure (Pa,O2) or O2 content (Ca,O2)? Thus, cardiac output (dye dilution with Cardio-green), leg blood flow (thermodilution), intra-arterial blood pressure and femoral arterial-to-venous differences in blood gases were determined in nine lowlanders studied during incremental exercise using a large (two-legged cycle ergometer exercise: Bike) and a small (one-legged knee extension exercise: Knee)muscle mass in normoxia, acute hypoxia (AH) (FIO2 = 0.105) and after 9 weeks of residence at 5260 m (CH). Reducing the size of the active muscle mass blunted by 62% the effect of hypoxia on VO2,peak in AH and abolished completely the effect of hypoxia on VO2,peak after altitude acclimatization. Acclimatization improved Bike peak exercise Pa,O2 from 34 +/- 1 in AH to 45 +/- 1 mmHg in CH(P <0.05) and Knee Pa,O2 from 38 +/- 1 to 55 +/- 2 mmHg(P <0.05). Peak cardiac output and leg blood flow were reduced in hypoxia only during Bike. Acute hypoxia resulted in reduction of systemic O2 delivery (46 and 21%) and leg O2 delivery (47 and 26%) during Bike and Knee, respectively, almost matching the corresponding reduction in VO2,peak. Altitude acclimatization restored fully peak systemic and leg O(2) delivery in CH (2.69 +/- 0.27 and 1.28 +/- 0.11 l min(-1), respectively) to sea level values (2.65 +/- 0.15 and 1.16 +/- 0.11 l min(-1), respectively) during Knee, but not during Bike. During Knee in CH, leg oxygen delivery was similar to normoxia and, therefore, also VO2,peak in spite of a Pa,O2 of 55 mmHg. Reducing the size of the active mass improves pulmonary gas exchange during hypoxic exercise, attenuates the Bohr effect on oxygen uploading at the lungs and preserves sea level convective O2 transport to the active muscles. Thus, the altitude-acclimatized human has potentially a similar exercising capacity as at sea level when the exercise model allows for an adequate oxygen delivery (blood flow x Ca,O2), with only a minor role of Pa,O2 per se, when Pa,O2 is more than 55 mmHg.
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Affiliation(s)
- José A L Calbet
- The Copenhagen Muscle Research Centre, Rigshospitalet, Copenhagen N, Denmark.
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Bärtsch P, Saltin B. General introduction to altitude adaptation and mountain sickness. Scand J Med Sci Sports 2008; 18 Suppl 1:1-10. [DOI: 10.1111/j.1600-0838.2008.00827.x] [Citation(s) in RCA: 140] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Calbet JA, Robach P, Lundby C, Boushel R. Is pulmonary gas exchange during exercise in hypoxia impaired with the increase of cardiac output? Appl Physiol Nutr Metab 2008; 33:593-600. [DOI: 10.1139/h08-010] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During exercise in humans, the alveolar–arterial O2 tension difference ((A–a)DO2) increases with exercise intensity and is an important factor determining the absolute level of oxygen binding to hemoglobin and therefore the level of systemic oxygen transport. During exercise in hypoxia, the (A–a)DO2 is accentuated. Using the multiple inert gas elimination technique it has been shown that during exercise in acute hypoxia the contribution of ventilation–perfusion inequality to (A–a)DO2 is rather small and in the absence of pulmonary edema intrapulmonary shunts can be ruled out. This implies that the main mechanism limiting pulmonary gas exchange is diffusion limitation. It is presumed that an elevation of cardiac output during exercise in acute hypoxia should increase the (A–a)DO2. However, no studies have examined how variations in cardiac output independently affect pulmonary diffusion with increases in exercise intensity. We have consistently observed that during steady-state, submaximal (100–120 W) exercise on the cycle ergometer in hypoxia the lung can accommodate an increase in cardiac output of ~2 L·min–1 without any significant effect on pulmonary gas exchange. This result contrasts with the predicted effect of cardiac output on (A–a)DO2 using the model of Piiper and Scheid, and thus indicates that an elevation of cardiac output is not necessarily accompanied by a reduction of mean transit time and (or) diffusion limitation during submaximal exercise in acute hypoxia. It remains to be determined what is the influence of changes in cardiac output per se on pulmonary gas exchange during high-intensity exercise.
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Affiliation(s)
- José A.L. Calbet
- Department of Physical Education, University of Las Palmas de Gran Canaria, 35017, Spain
- The Copenhagen Muscle Research Centre, Rigshospitalet, Denmark
- École Nationale de Ski et d’Alpinisme, Chamonix, France
- Laboratoire “Réponses cellulaires et fonctionnelles à l’hypoxie”, EA 2363, Université Paris 13, Bobigny, France
- Department of Sport Science, Århus Universitet, Katrinebjergvej 89C, Denmark
| | - Paul Robach
- Department of Physical Education, University of Las Palmas de Gran Canaria, 35017, Spain
- The Copenhagen Muscle Research Centre, Rigshospitalet, Denmark
- École Nationale de Ski et d’Alpinisme, Chamonix, France
- Laboratoire “Réponses cellulaires et fonctionnelles à l’hypoxie”, EA 2363, Université Paris 13, Bobigny, France
- Department of Sport Science, Århus Universitet, Katrinebjergvej 89C, Denmark
| | - Carsten Lundby
- Department of Physical Education, University of Las Palmas de Gran Canaria, 35017, Spain
- The Copenhagen Muscle Research Centre, Rigshospitalet, Denmark
- École Nationale de Ski et d’Alpinisme, Chamonix, France
- Laboratoire “Réponses cellulaires et fonctionnelles à l’hypoxie”, EA 2363, Université Paris 13, Bobigny, France
- Department of Sport Science, Århus Universitet, Katrinebjergvej 89C, Denmark
| | - Robert Boushel
- Department of Physical Education, University of Las Palmas de Gran Canaria, 35017, Spain
- The Copenhagen Muscle Research Centre, Rigshospitalet, Denmark
- École Nationale de Ski et d’Alpinisme, Chamonix, France
- Laboratoire “Réponses cellulaires et fonctionnelles à l’hypoxie”, EA 2363, Université Paris 13, Bobigny, France
- Department of Sport Science, Århus Universitet, Katrinebjergvej 89C, Denmark
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Rådegran G. Exercise limb blood flow response to acute and chronic hypoxia in Danish lowlanders and Aymara natives. Acta Physiol (Oxf) 2008; 192:531-9. [PMID: 17973951 DOI: 10.1111/j.1748-1716.2007.01768.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM The femoral artery blood flow response to submaximal, one-legged, dynamic, knee-extensor exercise was determined in acute and chronic hypoxia to investigate the hypotheses that with adaptation to chronic hypoxia blood haemoglobin increases, allowing preservation of blood flow as in normoxia. METHODS Sixteen Danish lowlanders participated, in groups of six to eight, in the experiments at sea level normoxia (FiO2 congruent with 0.21) and acute hypoxia (FiO2 congruent with 0.11), and chronic hypoxia after approximately 7 and 9-10 weeks at approximately 5260 m altitude breathing ambient air (FiO2 congruent with 0.21) or a hyperoxic gas (FiO2 congruent with 0.55). The response was compared with that in six Aymara natives. RESULTS The haemoglobin and haematocrit increased (P < 0.003) in the lowlanders at altitude vs. at sea level by approximately 39 and 27% respectively; i.e. to a similar (P = ns) level as in the natives. At rest, blood flow was the same (P = ns) in the lowlanders at sea level and altitude, as in the natives at altitude. During the onset of and incremental exercise, blood flow was the same (P = ns) in the lowlanders at sea level and altitude, as in the natives at altitude. Acute hypoxia increased (P < 0.05) blood flow by approximately 55% during exercise in the lowlanders at sea level. Acute hyperoxia decreased (P < 0.05) blood flow by approximately 22-29% during exercise in the lowlanders and natives at altitude. CONCLUSION In chronic hypoxia, blood haemoglobin increases, allowing normalization of the elevated exercise blood flow response in acute hypoxia, and preservation of the kinetics and steady-state exercise blood flow as in normoxia, being similar as in the natives at altitude.
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Affiliation(s)
- G Rådegran
- The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
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Lundby C, Boushel R, Robach P, Møller K, Saltin B, Calbet JAL. During hypoxic exercise some vasoconstriction is needed to match O2 delivery with O2 demand at the microcirculatory level. J Physiol 2007; 586:123-30. [PMID: 17932136 DOI: 10.1113/jphysiol.2007.146035] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
To test the hypothesis that the increased sympathetic tonus elicited by chronic hypoxia is needed to match O(2) delivery with O(2) demand at the microvascular level eight male subjects were investigated at 4559 m altitude during maximal exercise with and without infusion of ATP (80 mug (kg body mass)(-1) min(-1)) into the right femoral artery. Compared to sea level peak leg vascular conductance was reduced by 39% at altitude. However, the infusion of ATP at altitude did not alter femoral vein blood flow (7.6 +/- 1.0 versus 7.9 +/- 1.0 l min(-1)) and femoral arterial oxygen delivery (1.2 +/- 0.2 versus 1.3 +/- 0.2 l min(-1); control and ATP, respectively). Despite the fact that with ATP mean arterial blood pressure decreased (106.9 +/- 14.2 versus 83.3 +/- 16.0 mmHg, P < 0.05), peak cardiac output remained unchanged. Arterial oxygen extraction fraction was reduced from 85.9 +/- 5.3 to 72.0 +/- 10.2% (P < 0.05), and the corresponding venous O(2) content was increased from 25.5 +/- 10.0 to 46.3 +/- 18.5 ml l(-1) (control and ATP, respectively, P < 0.05). With ATP, leg arterial-venous O(2) difference was decreased (P < 0.05) from 139.3 +/- 9.0 to 116.9 +/- 8.4(-1) and leg .VO(2max) was 20% lower compared to the control trial (1.1 +/- 0.2 versus 0.9 +/- 0.1 l min(-1)) (P = 0.069). In summary, at altitude, some degree of vasoconstriction is needed to match O(2) delivery with O(2) demand. Peak cardiac output at altitude is not limited by excessive mean arterial pressure. Exercising leg .VO(2peak) is not limited by restricted vasodilatation in the altitude-acclimatized human.
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Affiliation(s)
- Carsten Lundby
- Copenhagen Muscle Research Center, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen Ø, Denmark.
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Schuler B, Thomsen JJ, Gassmann M, Lundby C. Timing the arrival at 2340 m altitude for aerobic performance. Scand J Med Sci Sports 2007; 17:588-94. [PMID: 17316377 DOI: 10.1111/j.1600-0838.2006.00611.x] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This study tested the hypothesis that maximal oxygen uptake (VO(2max)) and performance increase upon altitude acclimatization at moderate altitude. Eight elite cyclists were studied at sea level, and after 1 (Day 1), 7 (Day 7), 14 (Day 14) and 21 (Day 21) days of exposure to 2340 m. Capillary blood samples were taken on these days before performing two consecutive maximal exercise trials. Acclimatization increased hemoglobin concentration and arterial oxygen content. On Day 1, VO(2max) and time to exhaustion (at 80% of sea-level maximal power output) decreased by 12.8% (P<0.05) and 25.8% (P<0.05), respectively, compared with the corresponding sea-level values. Subsequently, these parameters increased by 3.2% (P<0.05) and 6.0% (P<0.05) from Days 1 to 7, by 4.8% (P<0.05) and 5.7% (P<0.05) from Days 7 to 14, followed by 0.7% (P>0.05) and 1.4% (P>0.05) from Days 14 to 21, respectively. These data suggest that endurance athletes competing at altitudes around 2340 m should expose themselves to this altitude at least 14 days before competition.
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Affiliation(s)
- B Schuler
- Institute of Veterinary Physiology, Vetsuisse Faculty and Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland
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Berger NJA, Campbell IT, Wilkerson DP, Jones AM. Influence of acute plasma volume expansion on V̇o2 kinetics, V̇o2peak, and performance during high-intensity cycle exercise. J Appl Physiol (1985) 2006; 101:707-14. [PMID: 16690793 DOI: 10.1152/japplphysiol.00154.2006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to examine the influence of acute plasma volume expansion (APVE) on oxygen uptake (V̇o2) kinetics, V̇o2peak, and time to exhaustion during severe-intensity exercise. Eight recreationally active men performed “step” cycle ergometer exercise tests at a work rate requiring 70% of the difference between the gas-exchange threshold and V̇o2max on three occasions: twice as a “control” (Con) and once after intravenous infusion of a plasma volume expander (Gelofusine; 7 ml/kg body mass). Pulmonary gas exchange was measured breath by breath. APVE resulted in a significant reduction in hemoglobin concentration (preinfusion: 16.0 ± 1.0 vs. postinfusion: 14.7 ± 0.8 g/dl; P < 0.001) and hematocrit (preinfusion: 44 ± 2 vs. postinfusion: 41 ± 3%; P < 0.01). Despite this reduction in arterial O2 content, APVE had no effect on V̇o2 kinetics (phase II time constant, Con: 33 ± 15 vs. APVE: 34 ± 12 s; P = 0.74), and actually resulted in an increased V̇o2peak (Con: 3.90 ± 0.56 vs. APVE: 4.12 ± 0.55 l/min; P = 0.006) and time to exhaustion (Con: 365 ± 58 vs. APVE: 424 ± 64 s; P = 0.04). The maximum O2 pulse was also enhanced by the treatment (Con: 21.3 ± 3.4 vs. APVE: 22.7 ± 3.4 ml/beat; P = 0.04). In conclusion, APVE does not alter V̇o2 kinetics but enhances V̇o2peak and exercise tolerance during high-intensity cycle exercise in young recreationally active subjects.
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Affiliation(s)
- Nicolas J A Berger
- Department of Exercise and Sports Science, Manchester Metropolitan University, Alsager, UK
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Stickland MK, Welsh RC, Haykowsky MJ, Petersen SR, Anderson WD, Taylor DA, Bouffard M, Jones RL. Effect of acute increases in pulmonary vascular pressures on exercise pulmonary gas exchange. J Appl Physiol (1985) 2006; 100:1910-7. [PMID: 16514002 DOI: 10.1152/japplphysiol.01484.2005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to determine the effect of acute increases in pulmonary vascular pressures, caused by the application of lower-body positive pressure (LBPP), on exercise alveolar-to-arterial Po2 difference (A-aDo2), anatomical intrapulmonary (IP) shunt recruitment, and ventilation. Eight healthy men performed graded upright cycling to 90% maximal oxygen uptake under normal conditions and with 52 Torr (1 psi) of LBPP. Pulmonary arterial (PAP) and pulmonary artery wedge pressures (PAWP) were measured with a Swan-Ganz catheter. Arterial blood samples were obtained from a radial artery catheter, cardiac output was calculated by the direct Fick method, and anatomical IP shunt was determined by administering agitated saline during continuous two-dimensional echocardiography. LBPP increased both PAP and PAWP while upright at rest, and at all points during exercise (mean increase in PAP and PAWP 3.7 and 4.0 mmHg, respectively, P < 0.05). There were no differences in exercise oxygen uptake or cardiac output between control and LBPP. Despite the increased PAP and PAWP with LBPP, A-aDo2 was not affected. In the upright resting position, there was no evidence of shunt in the control condition, whereas LBPP caused shunt in one subject. At the lowest exercise workload (75 W), shunt occurred in three subjects during control and in four subjects with LBPP. LBPP did not affect IP shunt recruitment during subsequent higher workloads. Minute ventilation and arterial Pco2 were not consistently affected by LBPP. Therefore, small acute increases in pulmonary vascular pressures do not widen exercise A-aDo2 or consistently affect IP shunt recruitment or ventilation.
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Affiliation(s)
- Michael K Stickland
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Canada.
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Calbet JAL, Lundby C, Koskolou M, Boushel R. Importance of hemoglobin concentration to exercise: acute manipulations. Respir Physiol Neurobiol 2006; 151:132-40. [PMID: 16516566 DOI: 10.1016/j.resp.2006.01.014] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2005] [Revised: 01/22/2006] [Accepted: 01/27/2006] [Indexed: 11/16/2022]
Abstract
An acute reduction of blood hemoglobin concentration ([Hb]), even when the circulating blood volume is maintained, results in lower (.)V(O(2)(max) and endurance performance, due to the reduction of the oxygen carrying capacity of blood. Conversely, an increase of [Hb] is associated with enhanced (.)V(O(2)(max) and endurance capacity, that is also proportional to the increase in the oxygen carrying capacity of blood. The effects on endurance capacity appear more pronounced and prolonged than on (.)V(O(2)(max). During submaximal exercise, there is a tight coupling between O(2) demand and O(2) delivery, such that if [Hb] is acutely decreased muscle blood flow is increased proportionally and vice versa. During maximal exercise with either a small or a large muscle mass, neither peak cardiac output nor peak leg blood flow are affected by reduced [Hb]. An acute increase of [Hb] has no effect on maximal exercise capacity or (.)V(O(2)(max) during exercise in acute hypoxia. Likewise, reducing [Hb] in altitude-acclimatized humans to pre-acclimatization values has no effect on (.)V(O(2)(max) during exercise in hypoxia.
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Affiliation(s)
- José A L Calbet
- Department of Physical Education, University of Las Palmas de Gran Canaria, Spain.
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Calbet JAL, Boushel R, Lundby C. Comment on Point:Counterpoint “Positive effects of intermittent hypoxia (live high:train low) on exercise performance are/are not mediated primarily by augmented red cell volume”. J Appl Physiol (1985) 2006; 100:749. [PMID: 16421283 DOI: 10.1152/japplphysiol.01119.2005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Noakes TD, Calbet JAL, Boushel R, Søndergaard H, Rådegran G, Wagner PD, Saltin B. Central regulation of skeletal muscle recruitment explains the reduced maximal cardiac output during exercise in hypoxia. Am J Physiol Regul Integr Comp Physiol 2004; 287:R996-9; author reply R999-1002. [PMID: 15371281 DOI: 10.1152/ajpregu.00608.2003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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