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Tymko MM, Young D, Vergel D, Matenchuk BA, Maier LE, Sivak A, Davenport MH, Steinback CD. The effect of hypoxemia on muscle sympathetic nerve activity and cardiovascular function: a systematic review and meta-analysis. Am J Physiol Regul Integr Comp Physiol 2023; 325:R474-R489. [PMID: 37642283 DOI: 10.1152/ajpregu.00021.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 08/01/2023] [Accepted: 08/08/2023] [Indexed: 08/31/2023]
Abstract
We conducted a systematic review and meta-analysis to determine the effect of acute poikilocapnic, high-altitude, and acute isocapnia hypoxemia on muscle sympathetic nerve activity (MSNA) and cardiovascular function. A comprehensive search across electronic databases was performed until June 2021. All observational designs were included: population (healthy individuals); exposures (MSNA during hypoxemia); comparators (hypoxemia severity and duration); outcomes (MSNA; heart rate, HR; and mean arterial pressure, MAP). Sixty-one studies were included in the meta-analysis. MSNA burst frequency increased by a greater extent during high-altitude hypoxemia [P < 0.001; mean difference (MD), +22.5 bursts/min; confidence interval (CI) = -19.20 to 25.84] compared with acute poikilocapnic hypoxemia (P < 0.001; MD, +5.63 bursts/min; CI = -4.09 to 7.17) and isocapnic hypoxemia (P < 0.001; MD, +4.72 bursts/min; CI = -3.37 to 6.07). MSNA burst amplitude was only elevated during acute isocapnic hypoxemia (P = 0.03; standard MD, +0.46 au; CI = -0.03 to 0.90), and MSNA burst incidence was only elevated during high-altitude hypoxemia [P < 0.001; MD, 33.05 bursts/100 heartbeats; CI = -28.59 to 37.51]. Meta-regression analysis indicated a strong relationship between MSNA burst frequency and hypoxemia severity for acute isocapnic studies (P < 0.001) but not acute poikilocapnia (P = 0.098). HR increased by the same extent across each type of hypoxemia [P < 0.001; MD +13.81 heartbeats/min; 95% CI = 12.59-15.03]. MAP increased during high-altitude hypoxemia (P < 0.001; MD, +5.06 mmHg; CI = 3.14-6.99), and acute isocapnic hypoxemia (P < 0.001; MD, +1.91 mmHg; CI = 0.84-2.97), but not during acute poikilocapnic hypoxemia (P = 0.95). Both hypoxemia type and severity influenced sympathetic nerve and cardiovascular function. These data are important for the better understanding of healthy human adaptation to hypoxemia.
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Affiliation(s)
- Michael M Tymko
- Integrative Cerebrovascular and Environmental Physiology SB Laboratory, Department of Human Health and Nutritional Sciences, College of Biological Science, University of Guelph, Guelph, Ontario, Canada
- Department of Medicine, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, & Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Desmond Young
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, & Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Daniel Vergel
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, & Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Brittany A Matenchuk
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, & Recreation, University of Alberta, Edmonton, Alberta, Canada
- Program for Pregnancy and Postpartum Health, Faculty of Kinesiology, Sports and Recreation, Women and Children's Health Research Institute, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Lauren E Maier
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, & Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Allison Sivak
- H.T. Coutts Education and Physical Education Library, University of Alberta, Edmonton, Alberta, Canada
| | - Margie H Davenport
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, & Recreation, University of Alberta, Edmonton, Alberta, Canada
- Program for Pregnancy and Postpartum Health, Faculty of Kinesiology, Sports and Recreation, Women and Children's Health Research Institute, Alberta Diabetes Institute, University of Alberta, Edmonton, Alberta, Canada
| | - Craig D Steinback
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, & Recreation, University of Alberta, Edmonton, Alberta, Canada
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DeLorey DS, Clifford PS. Does sympathetic vasoconstriction contribute to metabolism: Perfusion matching in exercising skeletal muscle? Front Physiol 2022; 13:980524. [PMID: 36171966 PMCID: PMC9510655 DOI: 10.3389/fphys.2022.980524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 08/17/2022] [Indexed: 11/14/2022] Open
Abstract
The process of matching skeletal muscle blood flow to metabolism is complex and multi-factorial. In response to exercise, increases in cardiac output, perfusion pressure and local vasodilation facilitate an intensity-dependent increase in muscle blood flow. Concomitantly, sympathetic nerve activity directed to both exercising and non-active muscles increases as a function of exercise intensity. Several studies have reported the presence of tonic sympathetic vasoconstriction in the vasculature of exercising muscle at the onset of exercise that persists through prolonged exercise bouts, though it is blunted in an exercise-intensity dependent manner (functional sympatholysis). The collective evidence has resulted in the current dogma that vasoactive molecules released from skeletal muscle, the vascular endothelium, and possibly red blood cells produce local vasodilation, while sympathetic vasoconstriction restrains vasodilation to direct blood flow to the most metabolically active muscles/fibers. Vascular smooth muscle is assumed to integrate a host of vasoactive signals resulting in a precise matching of muscle blood flow to metabolism. Unfortunately, a critical review of the available literature reveals that published studies have largely focused on bulk blood flow and existing experimental approaches with limited ability to reveal the matching of perfusion with metabolism, particularly between and within muscles. This paper will review our current understanding of the regulation of sympathetic vasoconstriction in contracting skeletal muscle and highlight areas where further investigation is necessary.
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Affiliation(s)
- Darren S. DeLorey
- Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, AB, Canada
- *Correspondence: Darren S. DeLorey,
| | - Philip S. Clifford
- College of Applied Health Sciences, University of Illinois at Chicago, Chicago, IL, United States
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Hansen AB, Amin SB, Hofstätter F, Mugele H, Simpson LL, Gasho C, Dawkins TG, Tymko MM, Ainslie PN, Villafuerte FC, Hearon CM, Lawley JS, Moralez G. Global Reach 2018: sympathetic neural and hemodynamic responses to submaximal exercise in Andeans with and without chronic mountain sickness. Am J Physiol Heart Circ Physiol 2022; 322:H844-H856. [PMID: 35333117 PMCID: PMC9018046 DOI: 10.1152/ajpheart.00555.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 03/14/2022] [Accepted: 03/14/2022] [Indexed: 11/22/2022]
Abstract
Andeans with chronic mountain sickness (CMS) and polycythemia have similar maximal oxygen uptakes to healthy Andeans. Therefore, this study aimed to explore potential adaptations in convective oxygen transport, with a specific focus on sympathetically mediated vasoconstriction of nonactive skeletal muscle. In Andeans with (CMS+, n = 7) and without (CMS-, n = 9) CMS, we measured components of convective oxygen delivery, hemodynamic (arterial blood pressure via intra-arterial catheter), and autonomic responses [muscle sympathetic nerve activity (MSNA)] at rest and during steady-state submaximal cycling exercise [30% and 60% peak power output (PPO) for 5 min each]. Cycling caused similar increases in heart rate, cardiac output, and oxygen delivery at both workloads between both Andean groups. However, at 60% PPO, CMS+ had a blunted reduction in Δtotal peripheral resistance (CMS-, -10.7 ± 3.8 vs. CMS+, -4.9 ± 4.1 mmHg·L-1·min-1; P = 0.012; d = 1.5) that coincided with a greater Δforearm vasoconstriction (CMS-, -0.2 ± 0.6 vs. CMS+, 1.5 ± 1.3 mmHg·mL-1·min-1; P = 0.008; d = 1.7) and a rise in Δdiastolic blood pressure (CMS-, 14.2 ± 7.2 vs. CMS+, 21.6 ± 4.2 mmHg; P = 0.023; d = 1.2) compared with CMS-. Interestingly, although MSNA burst frequency did not change at 30% or 60% of PPO in either group, at 60% Δburst incidence was attenuated in CMS+ (P = 0.028; d = 1.4). These findings indicate that in Andeans with polycythemia, light intensity exercise elicited similar cardiovascular and autonomic responses compared with CMS-. Furthermore, convective oxygen delivery is maintained during moderate-intensity exercise despite higher peripheral resistance. In addition, the elevated peripheral resistance during exercise was not mediated by greater sympathetic neural outflow, thus other neural and/or nonneural factors are perhaps involved.NEW & NOTEWORTHY During submaximal exercise, convective oxygen transport is maintained in Andeans suffering from polycythemia. Light intensity exercise elicited similar cardiovascular and autonomic responses compared with healthy Andeans. However, during moderate-intensity exercise, we observed a blunted reduction in total peripheral resistance, which cannot be ascribed to an exaggerated increase in muscle sympathetic nerve activity, indicating possible contributions from other neural and/or nonneural mechanisms.
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Affiliation(s)
- Alexander B Hansen
- Division of Performance, Physiology and Prevention, Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Sachin B Amin
- Division of Performance, Physiology and Prevention, Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Florian Hofstätter
- Division of Performance, Physiology and Prevention, Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Hendrik Mugele
- Division of Performance, Physiology and Prevention, Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Lydia L Simpson
- Division of Performance, Physiology and Prevention, Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Christopher Gasho
- Division of Pulmonary and Critical Care, Department of Medicine, University of Loma Linda, Loma Linda, California
| | - Tony G Dawkins
- Cardiff School of Sport and Health Sciences, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Michael M Tymko
- Physical Activity and Diabetes Laboratory, Faculty of Kinesiology and Recreation, University of Alberta, Edmonton, Alberta, Canada
- Centre of Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Philip N Ainslie
- Centre of Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Francisco C Villafuerte
- Laboratorio de Fisiología Comparada/Fisiología del Transporte de Oxígeno Facultad de Ciencias y Filosofía, Universidad Peruana Cayetano Heredia, Lima, Peru
| | - Christopher M Hearon
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Dallas, Dallas, Texas
| | - Justin S Lawley
- Division of Performance, Physiology and Prevention, Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Gilbert Moralez
- Department of Applied Clinical Research, University of Texas Southwestern Medical Center, Dallas, Texas
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Foster GE, Shafer BM, Shing C. An open-source application for the standardized burst identification from the integrated muscle sympathetic neurogram. J Neurophysiol 2021; 126:1831-1841. [PMID: 34705589 DOI: 10.1152/jn.00397.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Muscle sympathetic nerve activity (MSNA) can be acquired from humans using the technique of microneurography. The resulting integrated neurogram displays pulse-synchronous bursts of sympathetic activity, which undergoes processing for standard MSNA metrics including burst frequency, height, area, incidence, total activity, and latency. The procedure for detecting bursts of MSNA and calculating burst metrics is tedious and differs widely among laboratories worldwide. We sought to develop an open-source, cross-platform web application that provides a standardized approach for burst identification and a tool to increase research reproducibility for those measuring MSNA. We compared the performance of this web application against a manual scoring approach under conditions of rest, chemoreflex activation (n = 9, 20-min isocapnic hypoxia), and metaboreflex activation (n = 13, 2-min isometric handgrip exercise and 4-min postexercise circulatory occlusion). The intraclass correlation coefficient (ICC) indicated good to strong agreement between scoring approaches for burst frequency (ICC = 0.92-0.99), incidence (ICC = 0.94-0.99), height (ICC = 0.76-0.88), total activity (ICC = 0.85-0.99), and latency (ICC = 0.97-0.99). Agreement with burst area was poor to moderate (ICC = 0.04-0.67) but changes in burst area were similar with chemoreflex and metaboreflex activation. Scoring using the web application was highly efficient and provided data visualization tools that expedited data processing and the analysis of MSNA. We recommend the open-source web application be adopted by the community for the analysis of MSNA.NEW & NOTEWORTHY The basic analysis of muscle sympathetic nerve activity (MSNA) requires the identification of pulse-synchronous bursts from the integrated neurogram before standard MSNA metrics can be quantified. This process is a time-consuming task requiring an experienced microneurographer to visually identify and manually label bursts. We developed an open-source, cross-platform application permitting a standardized approach for sympathetic burst identification and present the performance of this application against a manual scorer under basal conditions and during sympathoexcitatory stresses.
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Affiliation(s)
- Glen E Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Brooke M Shafer
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Conan Shing
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
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Katayama K, Dominelli PB, Foster GE, Kipp S, Leahy MG, Ishida K, Sheel AW. Respiratory modulation of sympathetic vasomotor outflow during graded leg cycling. J Appl Physiol (1985) 2021; 131:858-867. [PMID: 34197231 DOI: 10.1152/japplphysiol.00118.2021] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Respiratory modulation of sympathetic vasomotor outflow to skeletal muscles (muscle sympathetic nerve activity; MSNA) occurs in resting humans. Specifically, MSNA is highest at end-expiration and lowest at end-inspiration during quiet, resting breathing. We tested the hypothesis that within-breath modulation of MSNA would be amplified during graded leg cycling. Thirteen (n = 3 females) healthy young (age: 25.2 ± 4.7 yr) individuals completed all testing. MSNA (right median nerve) was measured at rest (baseline) and during semirecumbent cycle exercise at 40%, 60%, and 80% of maximal workload (Wmax). MSNA burst frequency (BF) was 20.0 ± 4.0 bursts/min at baseline and was not different during exercise at 40%Wmax (21.3 ± 3.7 bursts/min; P = 0.292). Thereafter, MSNA BF increased significantly compared with baseline (60%Wmax: 31.6 ± 5.8 bursts/min; P < 0.001, 80%Wmax: 44.7 ± 5.3 bursts/min; P < 0.001). At baseline and all exercise intensities, MSNA BF was lowest at end-inspiration and greatest at mid-to-end expiration. The within-breath change in MSNA BF (ΔMSNA BF; end-expiration minus end-inspiration) gradually increased from baseline to 60%Wmax leg cycling, but no further increase appeared at 80%Wmax exercise. Our results indicate that within-breath modulation of MSNA is amplified from baseline to moderate intensity during dynamic exercise in young healthy individuals, and that no further potentiation occurs at higher exercise intensities. Our findings provide an important extension of our understanding of respiratory influences on sympathetic vasomotor control.NEW & NOTEWORTHY Within-breath modulation of sympathetic vasomotor outflow to skeletal muscle (muscle sympathetic nerve activity; MSNA) occurs in spontaneously breathing humans at rest. It is unknown if respiratory modulation persists during dynamic whole body exercise. We found that MSNA burst frequency was lowest at end-inspiration and highest at mid-to-end expiration during rest and graded leg cycling. Respiratory modulation of sympathetic vasomotor outflow remains intact and is amplified during dynamic whole body exercise.
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Affiliation(s)
- Keisho Katayama
- Research Center of Health, Physical Fitness and Sports, Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Paolo B Dominelli
- Department of Kinesiology, University of Waterloo, Waterloo, Ontario, Canada
| | - Glen E Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada
| | - Shalaya Kipp
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Michael G Leahy
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Koji Ishida
- Research Center of Health, Physical Fitness and Sports, Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Andrew William Sheel
- School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada
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Sakamoto R, Katayose M, Yamada Y, Neki T, Kamoda T, Tamai K, Yamazaki K, Iwamoto E. High-but not moderate-intensity exercise acutely attenuates hypercapnia-induced vasodilation of the internal carotid artery in young men. Eur J Appl Physiol 2021; 121:2471-2485. [PMID: 34028613 DOI: 10.1007/s00421-021-04721-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Accepted: 05/15/2021] [Indexed: 10/21/2022]
Abstract
PURPOSE Exercise-induced increases in shear rate (SR) across different exercise intensities may differentially affect hypercapnia-induced vasodilation of the internal carotid artery (ICA), a potential index of cerebrovascular function. We aimed to elucidate the effects of exercise intensity on ICA SR during exercise and post-exercise hypercapnia-induced vasodilation of the ICA in young men. METHODS Twelve healthy men completed 30 min of cycling at moderate [MIE; 65 ± 5% of age-predicted maximal heart rate (HRmax)] and high (HIE; 85 ± 5% HRmax) intensities. Hypercapnia-induced vasodilation was induced by 3 min of hypercapnia (target end-tidal partial pressure of CO2 + 10 mmHg) and was assessed at pre-exercise, 5 min and 60 min after exercise. Doppler ultrasound was used to measure ICA diameter and blood velocity during exercise and hypercapnia tests. RESULTS SR was not altered during either exercise (interaction and main effects of time; both P > 0.05). ICA conductance decreased during HIE from resting values (5.1 ± 1.3 to 3.2 ± 1.0 mL·min-1·mmHg-1; P < 0.01) but not during MIE (5.0 ± 1.3 to 4.0 ± 0.8 mL·min-1·mmHg-1; P = 0.11). Consequently, hypercapnia-induced vasodilation declined immediately after HIE (6.9 ± 1.7% to 4.0 ± 1.4%; P < 0.01), but not after MIE (7.2 ± 2.1% to 7.3 ± 1.8%; P > 0.05). Sixty minutes after exercise, hypercapnia-induced vasodilation returned to baseline values in both trials (MIE 8.0 ± 3.1%; HIE 6.4 ± 2.9%; both P > 0.05). CONCLUSION The present study showed blunted hypercapnia-induced vasodilation of the ICA immediately after high-intensity exercise, but not a moderate-intensity exercise in young men. Given that the acute response is partly linked to the adaptive response in the peripheral endothelial function, the effects of aerobic training on cerebrovascular health may vary depending on exercise intensity.
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Affiliation(s)
- Rintaro Sakamoto
- Department of Physical Therapy, Graduate School of Health Sciences, Sapporo Medical University, Sapporo, Japan
| | - Masaki Katayose
- School of Health Science, Sapporo Medical University, Sapporo, Japan
| | - Yutaka Yamada
- Department of Physical Therapy, Graduate School of Health Sciences, Sapporo Medical University, Sapporo, Japan
| | - Toru Neki
- School of Health Science, Sapporo Medical University, Sapporo, Japan
| | - Tatsuki Kamoda
- School of Health Science, Sapporo Medical University, Sapporo, Japan
| | - Katsuyuki Tamai
- School of Health Science, Sapporo Medical University, Sapporo, Japan
| | - Kotomi Yamazaki
- School of Health Science, Sapporo Medical University, Sapporo, Japan
| | - Erika Iwamoto
- School of Health Science, Sapporo Medical University, Sapporo, Japan.
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Sympathetic neural responses in heart failure during exercise and after exercise training. Clin Sci (Lond) 2021; 135:651-669. [DOI: 10.1042/cs20201306] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 02/01/2021] [Accepted: 02/15/2021] [Indexed: 12/25/2022]
Abstract
Abstract
The sympathetic nervous system coordinates the cardiovascular response to exercise. This regulation is impaired in both experimental and human heart failure with reduced ejection fraction (HFrEF), resulting in a state of sympathoexcitation which limits exercise capacity and contributes to adverse outcome. Exercise training can moderate sympathetic excess at rest. Recording sympathetic nerve firing during exercise is more challenging. Hence, data acquired during exercise are scant and results vary according to exercise modality. In this review we will: (1) describe sympathetic activity during various exercise modes in both experimental and human HFrEF and consider factors which influence these responses; and (2) summarise the effect of exercise training on sympathetic outflow both at rest and during exercise in both animal models and human HFrEF. We will particularly highlight studies in humans which report direct measurements of efferent sympathetic nerve traffic using intraneural recordings. Future research is required to clarify the neural afferent mechanisms which contribute to efferent sympathetic activation during exercise in HFrEF, how this may be altered by exercise training, and the impact of such attenuation on cardiac and renal function.
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Wan HY, Weavil JC, Thurston TS, Georgescu VP, Hureau TJ, Bledsoe AD, Buys MJ, Jessop JE, Richardson RS, Amann M. The exercise pressor reflex and chemoreflex interaction: cardiovascular implications for the exercising human. J Physiol 2020; 598:2311-2321. [PMID: 32170732 DOI: 10.1113/jp279456] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 03/10/2020] [Indexed: 01/11/2023] Open
Abstract
KEY POINTS Although the exercise pressor reflex (EPR) and the chemoreflex (CR) are recognized for their sympathoexcitatory effect, the cardiovascular implication of their interaction remains elusive. We quantified the individual and interactive cardiovascular consequences of these reflexes during exercise and revealed various modes of interaction. The EPR and hypoxia-induced CR interaction is hyper-additive for blood pressure and heart rate (responses during co-activation of the two reflexes are greater than the summation of the responses evoked by each reflex) and hypo-additive for peripheral haemodynamics (responses during co-activation of the reflexes are smaller than the summated responses). The EPR and hypercapnia-induced CR interaction results in a simple addition of the individual responses to each reflex (i.e. additive interaction). Collectively, EPR:CR co-activation results in significant cardiovascular interactions with restriction in peripheral haemodynamics, resulting from the EPR:CR interaction in hypoxia, likely having the most crucial impact on the functional capacity of an exercising human. ABSTRACT We investigated the interactive effect of the exercise pressor reflex (EPR) and the chemoreflex (CR) on the cardiovascular response to exercise. Eleven healthy participants (5 females) completed a total of six bouts of single-leg knee-extension exercise (60% peak work rate, 4 min each) either with or without lumbar intrathecal fentanyl to attenuate group III/IV afferent feedback from lower limbs to modify the EPR, while breathing either ambient air, normocapnic hypoxia (Sa O2 ∼79%, Pa O2 ∼43 mmHg, Pa CO2 ∼33 mmHg, pH ∼7.39), or normoxic hypercapnia (Sa O2 ∼98%, Pa O2 ∼105 mmHg, Pa CO2 ∼50 mmHg, pH ∼7.26) to modify the CR. During co-activation of the EPR and the hypoxia-induced CR (O2 -CR), mean arterial pressure and heart rate were significantly greater, whereas leg blood flow and leg vascular conductance were significantly lower than the summation of the responses evoked by each reflex alone. During co-activation of the EPR and the hypercapnia-induced CR (CO2 -CR), the haemodynamic responses were not different from the summated responses to each reflex response alone (P ≥ 0.1). Therefore, while the interaction resulting from the EPR:O2 -CR co-activation is hyper-additive for blood pressure and heart rate, and hypo-additive for peripheral haemodynamics, the interaction resulting from the EPR:CO2 -CR co-activation is simply additive for all cardiovascular parameters. Thus, EPR:CR co-activation results in significant interactions between cardiovascular reflexes, with the impact differing when the CR activation is achieved by hypoxia or hypercapnia. Since the EPR:CR co-activation with hypoxia potentiates the pressor response and restricts blood flow to contracting muscles, this interaction entails the most functional impact on an exercising human.
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Affiliation(s)
- Hsuan-Yu Wan
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA
| | - Joshua C Weavil
- Geriatric Research, Education, and Clinical Center, Salt Lake City, UT, VAMC, USA
| | - Taylor S Thurston
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT, USA
| | - Vincent P Georgescu
- Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT, USA
| | - Thomas J Hureau
- Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
| | - Amber D Bledsoe
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA
| | - Michael J Buys
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA
| | - Jacob E Jessop
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA
| | - Russell S Richardson
- Geriatric Research, Education, and Clinical Center, Salt Lake City, UT, VAMC, USA.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT, USA.,Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
| | - Markus Amann
- Department of Anesthesiology, University of Utah, Salt Lake City, UT, USA.,Geriatric Research, Education, and Clinical Center, Salt Lake City, UT, VAMC, USA.,Department of Nutrition and Integrative Physiology, University of Utah, Salt Lake City, UT, USA.,Department of Internal Medicine, University of Utah, Salt Lake City, UT, USA
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9
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Busch SA, Simpson LL, Sobierajski F, Riske L, Ainslie PN, Willie CK, Stembridge M, Moore JP, Steinback CD. Muscle sympathetic reactivity to apneic and exercise stress in high-altitude Sherpa. Am J Physiol Regul Integr Comp Physiol 2020; 318:R493-R502. [PMID: 31913686 DOI: 10.1152/ajpregu.00119.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Lowland-dwelling populations exhibit persistent sympathetic hyperactivity at altitude that alters vascular function. High-altitude populations, such as Sherpa, have previously exhibited greater peripheral blood flow in response to acute stress than Lowlanders, which may be explained through lower sympathetic activity. Our purpose was to determine whether Sherpa exhibit lower sympathetic reactivity to stress than Lowlanders. Muscle sympathetic nerve activity (MSNA; microneurography) was measured at rest in Lowlanders (n = 14; age = 27 ± 6 yr) at 344 m and between 1 and 10 days at 5,050 m. Sherpa (age = 32 ± 11 yr) were tested at 5,050 m (n = 8). Neurovascular reactivity (i.e., change in MSNA patterns) was measured during maximal end-expiratory apnea, isometric hand grip (IHG; 30% maximal voluntary contraction for 2-min), and postexercise circulatory occlusion (PECO; 3 min). Burst frequency (bursts/min) and incidence (bursts/100 heartbeats) and total normalized SNA (arbitrary units/min) were analyzed at rest, immediately before apnea breakpoint, and during the last minute of IHG and PECO. Vascular responses to apnea, IHG, and PECO were also measured. MSNA reactivity to apnea was smaller in Sherpa than Lowlanders at 5,050 m, although blood pressure responses were similar between groups. MSNA increases in Lowlanders during apnea at 5,050 m were significantly lower than at 344 m (P < 0.05), indicating that a possible sympathetic ceiling was reached in Lowlanders at 5,050 m. MSNA increased similarly during IHG and PECO in Lowlanders at both 334 m and 5,050 m and in Sherpa at 5,050 m, while vascular changes (mean brachial arterial pressure, contralateral brachial flow and resistance) were similar between groups. Sherpa demonstrate overall lower sympathetic reactivity that may be a result of heightened vascular responsiveness to potential apneic stress at altitude.
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Affiliation(s)
- Stephen A Busch
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Lydia L Simpson
- School of Sport, Health, and Exercise Sciences, Bangor University, Bangor, United Kingdom
| | - Frances Sobierajski
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Laurel Riske
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Chris K Willie
- Centre for Heart, Lung, and Vascular Health, University of British Columbia Okanagan, Kelowna, British Columbia, Canada
| | - Mike Stembridge
- Cardiff Centre for Exercise and Health, Cardiff School of Sport and Health, Cardiff Metropolitan University, Cardiff, United Kingdom
| | - Jonathan P Moore
- School of Sport, Health, and Exercise Sciences, Bangor University, Bangor, United Kingdom
| | - Craig D Steinback
- Neurovascular Health Lab, Faculty of Kinesiology, Sport, and Recreation, University of Alberta, Edmonton, Alberta, Canada
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10
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Katayama K, Barbosa TC, Kaur J, Young BE, Nandadeva D, Ogoh S, Fadel PJ. Muscle pump-induced inhibition of sympathetic vasomotor outflow during low-intensity leg cycling is attenuated by muscle metaboreflex activation. J Appl Physiol (1985) 2020; 128:1-7. [DOI: 10.1152/japplphysiol.00639.2019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Muscle sympathetic nerve activity (MSNA) decreases during leg cycling at low intensity because of muscle pump-induced increases in venous return and loading of the cardiopulmonary baroreceptors. However, MSNA increases during leg cycling when exercise is above moderate intensity or for a long duration, suggesting that the sympathoinhibitory effect of the cardiopulmonary baroreflex can be overridden by a powerful sympathoexcitatory drive, such as the skeletal muscle metaboreflex. Therefore, we tested the hypothesis that high-intensity muscle metaboreflex activation attenuates muscle pump-induced inhibition of MSNA during leg cycling. MSNA (left radial nerve) was recorded during graded isolation of the muscle metaboreflex in the forearm with postexercise ischemia (PEI) after low (PEI-L)- and high (PEI-H)-intensity isometric handgrip exercise (20% and 40% maximum voluntary contraction, respectively). Leg cycling (15–20 W) was performed alone and during each PEI trial (PEI-L+Cycling, PEI-H+Cycling). Cycling alone induced a significant decrease in MSNA burst frequency (BF) and total activity (TA). MSNA BF and TA also decreased when cycling was performed during PEI-L. However, the magnitude of decrease in MSNA during PEI-L+Cycling [∆BF: –19 ± 2% ( P < 0.001), ∆TA: –25 ± 4% ( P < 0.001); mean ± SE] was less than that during cycling alone [∆BF: –39 ± 5% ( P = 0.003), ∆TA: –45 ± 5% ( P = 0.002)]. More importantly, MSNA did not decrease during cycling with PEI-H [∆BF: –1 ± 2% ( P = 0.845), ∆TA: +2 ± 3% ( P = 0.959)]. These results suggest that muscle pump-induced inhibition of sympathetic vasomotor outflow during low-intensity leg cycling is attenuated by muscle metaboreflex activation in an intensity-dependent manner. NEW & NOTEWORTHY There are no available data concerning the interaction between the sympathoinhibitory effect of muscle pump-induced cardiopulmonary baroreflex loading during leg cycling and the sympathoexcitatory influence of the muscle metaboreflex. In this study, muscle metaboreflex activation attenuated the inhibition of muscle sympathetic nerve activity (MSNA) during leg cycling. This may explain, in part, the response of MSNA to graded-intensity dynamic exercise in which low-intensity leg cycling inhibits MSNA whereas high-intensity exercise elicits graded sympathoexcitation.
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Affiliation(s)
- Keisho Katayama
- Research Center of Health, Physical Fitness, and Sports, Nagoya University, Nagoya, Japan
| | - Thales C. Barbosa
- Department of Kinesiology, University of Texas at Arlington, Arlington, Texas
| | - Jasdeep Kaur
- Department of Kinesiology, University of Texas at Arlington, Arlington, Texas
| | - Benjamin E. Young
- Department of Kinesiology, University of Texas at Arlington, Arlington, Texas
| | - Damsara Nandadeva
- Department of Kinesiology, University of Texas at Arlington, Arlington, Texas
| | - Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe, Japan
| | - Paul J. Fadel
- Department of Kinesiology, University of Texas at Arlington, Arlington, Texas
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11
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Notarius CF, Millar PJ, Keir DA, Murai H, Haruki N, O'Donnell E, Marzolini S, Oh P, Floras JS. Training heart failure patients with reduced ejection fraction attenuates muscle sympathetic nerve activation during mild dynamic exercise. Am J Physiol Regul Integr Comp Physiol 2019; 317:R503-R512. [PMID: 31365304 DOI: 10.1152/ajpregu.00104.2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Muscle sympathetic nerve activity (MSNA) decreases during low-intensity dynamic one-leg exercise in healthy subjects but increases in patients with heart failure with reduced ejection fraction (HFrEF). We hypothesized that increased peak oxygen uptake (V̇o2peak) after aerobic training would be accompanied by less sympathoexcitation during both mild and moderate one-leg dynamic cycling, an attenuated muscle metaboreflex, and greater skin vasodilation. We studied 27 stable, treated HFrEF patients (6 women; mean age: 65 ± 2 SE yr; mean left ventricular ejection fraction: 30 ± 1%) and 18 healthy age-matched volunteers (6 women; mean age: 57 ± 2 yr). We assessed V̇o2peak (open-circuit spirometry) and the skin microcirculatory response to reactive hyperemia (laser flowmetry). Fibular MSNA (microneurography) was recorded before and during one-leg cycling (2 min unloaded and 2 min at 50% of V̇o2peak) and, to assess the muscle metaboreflex, during posthandgrip ischemia (PHGI). HFrEF patients were evaluated before and after 6 mo of exercise-based cardiac rehabilitation. Pretraining V̇o2peak and skin vasodilatation were lower (P < 0.001) and resting MSNA higher (P = 0.01) in HFrEF than control subjects. Training improved V̇o2peak (+3.0 ± 1.0 mL·kg-1·min-1; P < 0.001) and cutaneous vasodilation and diminished resting MSNA (-6.0 ± 2.0, P = 0.01) plus exercise MSNA during unloaded (-4.0 ± 2.5, P = 0.04) but not loaded cycling (-1.0 ± 4.0 bursts/min, P = 0.34) and MSNA during PHGI (P < 0.05). In HFrEF patients, exercise training lowers MSNA at rest, desensitizes the sympathoexcitatory metaboreflex, and diminishes MSNA elicited by mild but not moderate cycling. Training-induced downregulation of resting MSNA and attenuated reflex sympathetic excitation may improve exercise capacity and survival.
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Affiliation(s)
- Catherine F Notarius
- Division of Cardiology, University Health Network and Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Philip J Millar
- Division of Cardiology, University Health Network and Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada.,Department of Human Health and Nutritional Sciences, University of Guelph, Ontario, Canada
| | - Daniel A Keir
- Division of Cardiology, University Health Network and Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Hisayoshi Murai
- Division of Cardiology, University Health Network and Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Nobuhiko Haruki
- Division of Cardiology, University Health Network and Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada
| | - Emma O'Donnell
- Division of Cardiology, University Health Network and Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada.,School of Sport, Exercise, and Health Sciences, Loughborough University, Loughborough, United Kingdom
| | - Susan Marzolini
- Cardiovascular Prevention and Rehabilitation Program, Toronto Rehabilitation Institute, University Health Network, Toronto, Ontario, Canada
| | - Paul Oh
- Cardiovascular Prevention and Rehabilitation Program, Toronto Rehabilitation Institute, University Health Network, Toronto, Ontario, Canada
| | - John S Floras
- Division of Cardiology, University Health Network and Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada
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12
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Katayama K, Saito M. Muscle sympathetic nerve activity during exercise. J Physiol Sci 2019; 69:589-598. [PMID: 31054082 PMCID: PMC10717921 DOI: 10.1007/s12576-019-00669-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 02/22/2019] [Indexed: 11/25/2022]
Abstract
Appropriate cardiovascular adjustment is necessary to meet the metabolic demands of working skeletal muscle during exercise. The sympathetic nervous system plays a crucial role in the regulation of arterial blood pressure and blood flow during exercise, and several important neural mechanisms are responsible for changes in sympathetic vasomotor outflow. Changes in sympathetic vasomotor outflow (i.e., muscle sympathetic nerve activity: MSNA) in inactive muscles during exercise differ depending on the exercise mode (static or dynamic), intensity, duration, and various environmental conditions (e.g., hot and cold environments or hypoxic). In 1991, Seals and Victor [6] reviewed MSNA responses to static and dynamic exercise with small muscle mass. This review provides an updated comprehensive overview on the MSNA response to exercise including large-muscle, dynamic leg exercise, e.g., two-legged cycling, and its regulatory mechanisms in healthy humans.
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Affiliation(s)
- Keisho Katayama
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, 464-8601, Japan.
- Graduate School of Medicine, Nagoya University, Nagoya, Japan.
| | - Mitsuru Saito
- Applied Physiology Laboratory, Toyota Technological Institute, Nagoya, Japan
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13
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Dominelli PB, Katayama K, Vermeulen TD, Stuckless TJ, Brown CV, Foster GE, Sheel AW. Work of breathing influences muscle sympathetic nerve activity during semi-recumbent cycle exercise. Acta Physiol (Oxf) 2019; 225:e13212. [PMID: 30358142 DOI: 10.1111/apha.13212] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 10/17/2018] [Accepted: 10/18/2018] [Indexed: 02/06/2023]
Abstract
Reducing the work of breathing during exercise improves locomotor muscle blood flow and reduces diaphragm and locomotor muscle fatigue and is thought to be the result of a sympathetically mediated reflex. AIM The aim of this study was to assess muscle sympathetic nerve activity (MSNA) when the work of breathing is experimentally lowered during dynamic exercise. METHODS Healthy subjects (n = 12; age = 29 ± 9 years) performed semi-recumbent cycling trials at 40%, 60%, and 80% of peak workload. Exercise trials consisted of spontaneous breathing, reduced work of breathing (proportional assist ventilator), followed by further spontaneous breathing (post-ventilator). MSNA was recorded from the median nerve. RESULTS There was no difference in work of breathing between PAV and post-PAV at 40% peak work. At 60% peak work, the ventilator significantly (P < 0.05) reduced work of breathing (103 ± 39 vs 144 ± 47 J min-1 ), sympathetic nerve activity (35 ± 5 vs 42 ± 8 burst min-1 ), and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mover><mml:mi>V</mml:mi> <mml:mo>˙</mml:mo></mml:mover> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:math> (2.4 ± 0.5 vs 2.6 ± 0.5 L min-1 ) without influencing ventilation (86 ± 9 vs 82 ± 10 L min-1 ; P > 0.05), for PAV and post-PAV respectively. During 80% peak work (n = 8), the ventilator significantly (P < 0.05) reduced work of breathing (235 ± 110 vs. 361 ± 150 J min-1 ), MSNA (48 ± 7 vs 54 ± 11 burst min-1 ), and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mover><mml:mi>V</mml:mi> <mml:mo>˙</mml:mo></mml:mover> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:math> (2.9 ± 0.6 vs 3.2 ± 0.7 L min-1 ) but not ventilation (121 ± 20 vs 123 ± 20 L min-1 ; P > 0.05), for PAV and post-PAV respectively. There was a significant relationship between MSNA and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:mover><mml:mi>V</mml:mi> <mml:mo>˙</mml:mo></mml:mover> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:math> (P < 0.0001) with a significant interaction due to the ventilator (P < 0.05). CONCLUSION Lowering the normally occurring work of breathing during exercise results in commensurate reductions in MSNA. Our findings provide evidence of a sympathetically mediated vasoconstrictor effect emanating from respiratory muscles during exercise.
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Affiliation(s)
- Paolo B. Dominelli
- School of Kinesiology University of British Columbia Vancouver British Columbia Canada
- Department of Anaesthesiology Mayo Clinic Rochester Minnesota
| | - Keisho Katayama
- Research Center of Health, Physical Fitness and Sports, Graduate School of Medicine Nagoya University Nagoya Japan
| | - Tyler D. Vermeulen
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences University of British Columbia Kelowna British Columbia Canada
| | - Troy J.R. Stuckless
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences University of British Columbia Kelowna British Columbia Canada
| | - Courtney V. Brown
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences University of British Columbia Kelowna British Columbia Canada
| | - Glen E. Foster
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences University of British Columbia Kelowna British Columbia Canada
| | - Andrew William Sheel
- School of Kinesiology University of British Columbia Vancouver British Columbia Canada
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14
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Notarius CF, Millar PJ, Doherty CJ, Incognito AV, Haruki N, O'Donnell E, Floras JS. Microneurographic characterization of sympathetic responses during 1-leg exercise in young and middle-aged humans. Appl Physiol Nutr Metab 2018; 44:194-199. [PMID: 30063163 DOI: 10.1139/apnm-2018-0101] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Muscle sympathetic nerve activity (MSNA) at rest increases with age. However, the influence of age on MSNA recorded during dynamic leg exercise is unknown. We tested the hypothesis that aging attenuates the sympatho-inhibitory response observed in young subjects performing mild to moderate 1-leg cycling. After predetermining peak oxygen uptake, we compared contra-lateral fibular nerve MSNA during 2 min each of mild (unloaded) and moderate (30%-40% of the work rate at peak oxygen uptake, halved for single leg) 1-leg cycling in 18 young (age, 23 ± 1 years (mean ± SE)) and 18 middle-aged (age, 57 ± 2 years) sex-matched healthy subjects. Mean height, weight, resting heart rate, systolic blood pressure, and percent predicted peak oxygen uptake were similar between groups. Middle-aged subjects had higher resting MSNA burst frequency and incidence (P < 0.001) and diastolic blood pressure (P = 0.04). During moderate 1-leg cycling, older subjects' systolic blood pressure increased more (+21 ± 5 vs. +10 ± 1 mm Hg; P = 0.02) and their fall in MSNA burst incidence was amplified (-19 ± 2 vs. -11 ± 2 bursts/100 heart beats; P = 0.01) but because heart rate rose less (+15 ± 3 vs. +19 ± 2 bpm; P = 0.03), exercise induced similar reductions in burst frequency (P = 0.25). Contrary to our initial hypothesis, with advancing age, mild- to moderate-intensity dynamic leg exercise elicits a greater rise in systolic blood pressure and a larger fall in MSNA.
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Affiliation(s)
- Catherine F Notarius
- a University Health Network and Mount Sinai Hospital Division of Cardiology, University of Toronto, Toronto General Hospital, University Health Network, 200 Elizabeth St., Toronto, ON M5G 2C4, Canada
| | - Philip J Millar
- a University Health Network and Mount Sinai Hospital Division of Cardiology, University of Toronto, Toronto General Hospital, University Health Network, 200 Elizabeth St., Toronto, ON M5G 2C4, Canada.,b Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Connor J Doherty
- b Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Anthony V Incognito
- b Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Nobuhiko Haruki
- a University Health Network and Mount Sinai Hospital Division of Cardiology, University of Toronto, Toronto General Hospital, University Health Network, 200 Elizabeth St., Toronto, ON M5G 2C4, Canada
| | - Emma O'Donnell
- a University Health Network and Mount Sinai Hospital Division of Cardiology, University of Toronto, Toronto General Hospital, University Health Network, 200 Elizabeth St., Toronto, ON M5G 2C4, Canada.,c School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough LE11 3TU, UK
| | - John S Floras
- a University Health Network and Mount Sinai Hospital Division of Cardiology, University of Toronto, Toronto General Hospital, University Health Network, 200 Elizabeth St., Toronto, ON M5G 2C4, Canada
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15
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Katayama K, Kaur J, Young BE, Barbosa TC, Ogoh S, Fadel PJ. High-intensity muscle metaboreflex activation attenuates cardiopulmonary baroreflex-mediated inhibition of muscle sympathetic nerve activity. J Appl Physiol (1985) 2018; 125:812-819. [PMID: 29672226 DOI: 10.1152/japplphysiol.00161.2018] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous studies have shown that muscle sympathetic nerve activity (MSNA) is reduced during low- and mild-intensity dynamic leg exercise. It has been suggested that such inhibition is mediated by loading of the cardiopulmonary baroreceptors and that this effect is overridden by muscle metaboreflex activation with higher-intensity exercise. However, limited data are available regarding the interaction between the cardiopulmonary baroreflex and the muscle metaboreflex. Therefore, we tested the hypothesis that cardiopulmonary baroreflex-mediated inhibition of MSNA is attenuated during high-intensity muscle metaboreflex activation. In nine young men, MSNA (right peroneal nerve), mean arterial pressure (MAP), and thoracic impedance were recorded. Graded isolation of muscle metaboreflex activation was achieved via postexercise ischemia (PEI) following low (PEI-L)-, moderate (PEI-M)-, and high (PEI-H)-intensity isometric handgrip performed at 20, 30, and 40% maximum voluntary contraction, respectively. Lower-body positive pressure (LBPP, +10 Torr) was applied at rest and during PEI, to load the cardiopulmonary baroreceptors. Handgrip exercise elicited intensity-dependent increases in MSNA and MAP that were maintained during PEI, indicating a graded muscle metaboreflex activation. LBPP at rest significantly decreased MSNA burst frequency (BF: -36.7 ± 4.7%, mean ± SE, P < 0.05), whereas MAP was unchanged. When LBPP was applied during PEI, MSNA BF decreased significantly at PEI-L (-40.0 ± 9.2%, P < 0.05) and PEI-M (-27.0 ± 6.3%, P < 0.05), but not at PEI-H (+1.9 ± 7.1%, P > 0.05). These results suggest that low- and moderate-intensity muscle metaboreflex activation does not modulate the inhibition of MSNA by cardiopulmonary baroreceptor loading, whereas high-intensity metaboreflex activation can override cardiopulmonary baroreflex-mediated inhibition of sympathetic vasomotor outflow. NEW & NOTEWORTHY The interaction between the sympathoinhibitory influence of cardiopulmonary baroreflex and sympathoexcitatory effect of skeletal muscle metaboreflex is not completely understood. In the current study, light- to moderate-intensity muscle metaboreflex activation did not modulate the suppression of muscle sympathetic nerve activity by cardiopulmonary baroreceptor loading, whereas high-intensity muscle metaboreflex activation attenuated the cardiopulmonary baroreflex-mediated inhibition of muscle sympathetic nerve activity. These results provide important information concerning the neural reflex mechanisms regulating sympathetic vasomotor outflow during exercise.
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Affiliation(s)
- Keisho Katayama
- Department of Kinesiology, University of Texas at Arlington , Arlington, Texas.,Research Center of Health, Physical Fitness and Sports, Nagoya University , Nagoya , Japan
| | - Jasdeep Kaur
- Department of Kinesiology, University of Texas at Arlington , Arlington, Texas
| | - Benjamin E Young
- Department of Kinesiology, University of Texas at Arlington , Arlington, Texas
| | - Thales C Barbosa
- Department of Kinesiology, University of Texas at Arlington , Arlington, Texas
| | - Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe, Japan
| | - Paul J Fadel
- Department of Kinesiology, University of Texas at Arlington , Arlington, Texas
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16
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Katayama K, Smith JR, Goto K, Shimizu K, Saito M, Ishida K, Koike T, Iwase S, Harms CA. Elevated sympathetic vasomotor outflow in response to increased inspiratory muscle activity during exercise is less in young women compared with men. Exp Physiol 2018; 103:570-580. [DOI: 10.1113/ep086817] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2017] [Accepted: 01/11/2018] [Indexed: 01/01/2023]
Affiliation(s)
- Keisho Katayama
- Research Center of Health, Physical Fitness and Sports; Nagoya University; Nagoya Japan
- Graduate School of Medicine; Nagoya University; Nagoya Japan
| | - Joshua R. Smith
- Department of Cardiovascular Diseases; Mayo Clinic; Rochester MN USA
| | - Kanako Goto
- Graduate School of Medicine; Nagoya University; Nagoya Japan
| | - Kaori Shimizu
- Graduate School of Education and Human Development; Nagoya University; Nagoya Japan
| | - Mitsuru Saito
- Applied Physiology Laboratory; Toyota Technological Institute; Nagoya Japan
| | - Koji Ishida
- Research Center of Health, Physical Fitness and Sports; Nagoya University; Nagoya Japan
- Graduate School of Medicine; Nagoya University; Nagoya Japan
| | - Teruhiko Koike
- Research Center of Health, Physical Fitness and Sports; Nagoya University; Nagoya Japan
- Graduate School of Medicine; Nagoya University; Nagoya Japan
| | - Satoshi Iwase
- Department of Physiology, School of Medicine; Aichi Medical University; Nagakute Japan
| | - Craig A. Harms
- Department of Kinesiology; Kansas State University; Manhattan KS USA
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17
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Tymko MM, Tremblay JC, Steinback CD, Moore JP, Hansen AB, Patrician A, Howe CA, Hoiland RL, Green DJ, Ainslie PN. UBC-Nepal Expedition: acute alterations in sympathetic nervous activity do not influence brachial artery endothelial function at sea level and high altitude. J Appl Physiol (1985) 2017; 123:1386-1396. [PMID: 28860174 DOI: 10.1152/japplphysiol.00583.2017] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 08/09/2017] [Accepted: 08/25/2017] [Indexed: 01/08/2023] Open
Abstract
Evidence indicates that increases in sympathetic nervous activity (SNA), and acclimatization to high altitude (HA), may reduce endothelial function as assessed by brachial artery flow-mediated dilatation (FMD); however, it is unclear whether such changes in FMD are due to direct vascular constraint, or consequential altered hemodynamics (e.g., shear stress) associated with increased SNA as a consequence of exposure to HA. We hypothesized that 1) at rest, SNA would be elevated and FMD would be reduced at HA compared with sea-level (SL); and 2) at SL and HA, FMD would be reduced when SNA was acutely increased, and elevated when SNA was acutely decreased. Using a novel, randomized experimental design, brachial artery FMD was assessed at SL (344 m) and HA (5,050 m) in 14 participants during mild lower-body negative pressure (LBNP; -10 mmHg) and lower-body positive pressure (LBPP; +10 mmHg). Blood pressure (finger photoplethysmography), heart rate (electrocardiogram), oxygen saturation (pulse oximetry), and brachial artery blood flow and shear rate (Duplex ultrasound) were recorded during LBNP, control, and LBPP trials. Muscle SNA was recorded (via microneurography) in a subset of participants (n = 5). Our findings were 1) at rest, SNA was elevated (P < 0.01), and absolute FMD was reduced (P = 0.024), but relative FMD remained unaltered (P = 0.061), at HA compared with SL; and 2) despite significantly altering SNA with LBNP (+60.3 ± 25.5%) and LBPP (-37.2 ± 12.7%) (P < 0.01), FMD was unaltered at SL (P = 0.448) and HA (P = 0.537). These data indicate that acute and mild changes in SNA do not directly influence brachial artery FMD at SL or HA.NEW & NOTEWORTHY The role of the sympathetic nervous system on endothelial function remains unclear. We used lower-body negative and positive pressure to manipulate sympathetic nervous activity at sea level and high altitude and measured brachial endothelial function via flow-mediated dilation. We found that acutely altering sympathetic nervous activity had no effect on endothelial function.
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Affiliation(s)
- Michael M Tymko
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada;
| | - Joshua C Tremblay
- Cardiovascular Stress Response Laboratory, School of Kinesiology and Health Studies, Queen's University, Kingston, Ontario, Canada
| | - Craig D Steinback
- Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta, Canada
| | - Jonathan P Moore
- Extremes Research Group, School of Sport, Health and Exercise Sciences, Bangor University, Gwynedd, United Kingdom
| | - Alex B Hansen
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | | | - Connor A Howe
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | - Ryan L Hoiland
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
| | - Daniel J Green
- School of Sports Science, Exercise and Health, The University of Western Australia, Crawley, Western Australia, Australia; and.,Research Institute for Sport and Exercise Science, Liverpool John Moores University, Liverpool, United Kingdom
| | - Philip N Ainslie
- Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Science, University of British Columbia, Kelowna, Canada
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18
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Katayama K, Ishida K, Saito M, Koike T, Ogoh S. Hypoxia attenuates cardiopulmonary reflex control of sympathetic nerve activity during mild dynamic leg exercise. Exp Physiol 2016; 101:377-86. [PMID: 27094223 DOI: 10.1113/ep085632] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 01/04/2016] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? The cardiopulmonary baroreflex inhibits adjustment of sympathetic vasomotor outflow during mild-intensity dynamic exercise. However, it is unclear how suppression of sympathetic vasomotor outflow by the cardiopulmonary baroreflex is modulated by a powerful sympatho-excitatory drive from the exercise pressor reflex, central command and/or the arterial chemoreflex. What is the main finding and its importance? Hypoxia-induced heightened sympathetic nerve activity during dynamic exercise attenuated cardiopulmonary baroreflex control of sympathetic vasomotor outflow. This could facilitate the redistribution of blood flow to the active muscles by sympathetically mediated vasoconstriction of inactive muscles. Muscle sympathetic nerve activity (MSNA) does not increase during mild-intensity dynamic leg exercise in normoxic conditions, despite activation of central command and the exercise pressor reflex. Suppression of MSNA could be caused by muscle pump-induced loading of cardiopulmonary baroreceptors. In contrast, MSNA increases during mild dynamic leg exercise in hypoxic conditions. We hypothesized that hypoxic exercise, which induces a powerful sympatho-excitatory drive from the exercise pressor reflex, central command and/or arterial chemoreflex, attenuates cardiopulmonary reflex control of sympathetic vasomotor outflow. To test this hypothesis, MSNA was recorded during leg cycling in hypoxic conditions and with increased central blood volume by increasing the pedalling frequency to change the cardiopulmonary baroreflex. Subjects performed two leg cycle exercises at different pedal cadences of 60 and 80 r.p.m. (60EX and 80EX trials, respectively) in two (haemodynamic and MSNA) measurement conditions while breathing a hypoxic gas mixture (inspired oxygen fraction = 0.12). Thoracic impedance, stroke volume and cardiac output were measured non-invasively using impedance cardiography. During the MSNA test, MSNA was recorded via microneurography at the right median nerve at the elbow. Changes in thoracic impedance, stroke volume and cardiac output during the 80EX trial were greater than those during the 60EX trial. The MSNA burst frequency during hypoxic exercise in the 80EX trial (39 ± 4 bursts min(-1)) did not differ from that during the 60EX trial (39 ± 3 bursts min(-1)). These results suggest that the cardiopulmonary baroreflex of sympathetic vasomotor outflow during dynamic exercise is modulated by heightened hypoxia-induced sympathetic nerve activity.
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Affiliation(s)
- Keisho Katayama
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan.,Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Koji Ishida
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan.,Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Mitsuru Saito
- Faculty of Psychological and Physical Science, Aichigakuin University, Nisshin, Japan
| | - Teruhiko Koike
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan.,Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe, Japan
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19
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Sato K, Iemitsu M, Katayama K, Ishida K, Kanao Y, Saito M. Responses of sex steroid hormones to different intensities of exercise in endurance athletes. Exp Physiol 2015; 101:168-75. [DOI: 10.1113/ep085361] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2015] [Accepted: 10/29/2015] [Indexed: 02/01/2023]
Affiliation(s)
- Koji Sato
- Faculty of Sport and Health Science; Ritsumeikan University; Kusatsu Japan
| | - Motoyuki Iemitsu
- Faculty of Sport and Health Science; Ritsumeikan University; Kusatsu Japan
| | - Keisho Katayama
- Research Center of Health, Physical Fitness and Sports; Nagoya University; Nagoya Japan
| | - Koji Ishida
- Research Center of Health, Physical Fitness and Sports; Nagoya University; Nagoya Japan
| | - Yoji Kanao
- Faculty of Sport and Health Science; Tokaigakuen University; Nagoya Japan
| | - Mitsuru Saito
- Faculty of Psychological and Physical Science; Aichigakuin University; Nisshin Japan
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20
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Morales-Artacho AJ, Padial P, Rodríguez-Matoso D, Rodríguez-Ruiz D, García-Ramos A, García-Manso JM, Calderón C, Feriche B. Assessment of Muscle Contractile Properties at Acute Moderate Altitude Through Tensiomyography. High Alt Med Biol 2015; 16:343-9. [PMID: 26562625 DOI: 10.1089/ham.2015.0078] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Under hypoxia, alterations in muscle contractile properties and faster fatigue development have been reported. This study investigated the efficacy of tensiomyography (TMG) in assessing muscle contractile function at acute moderate altitude. Biceps femoris (BF) and vastus lateralis (VL) muscles of 18 athletes (age 20.1 ± 6.1 years; body mass 65.4 ± 13.9 kg; height 174.6 ± 9.5 cm) were assessed at sea level and moderate altitude using electrically evoked contractions on two consecutive days. Maximum radial displacement (Dm), time of contraction (Tc), reaction time (Td), sustained contraction time (Ts), and relaxation time (Tr) were recorded at 40, 60, 80, and 100 mA. At altitude, VL showed lower Dm values at 40 mA (p = 0.008; ES = -0.237). Biceps femoris showed Dm decrements in all electrical stimulations (p < 0.001, ES > 0.61). In VL, Tc was longer at altitude at 40 (p = 0.031, ES = 0.56), and 100 mA (p = 0.03, ES = 0.51). Regarding Td, VL showed significant increases in all electrical intensities under hypoxia (p ≤ 0.03, ES ≥ 0.33). TMG appears effective at detecting slight changes in the muscle contractile properties at moderate altitude. Further research involving TMG along with other muscle function assessment methods is needed to provide additional insight into peripheral neuromuscular alterations at moderate altitude.
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Affiliation(s)
- Antonio J Morales-Artacho
- 1 Department of Physical Education and Sport, Faculty of Sport Sciences, University of Granada , Granada, Spain
| | - Paulino Padial
- 1 Department of Physical Education and Sport, Faculty of Sport Sciences, University of Granada , Granada, Spain
| | | | | | - Amador García-Ramos
- 1 Department of Physical Education and Sport, Faculty of Sport Sciences, University of Granada , Granada, Spain
| | | | - Carmen Calderón
- 3 Sport Performance Centre of Sierra Nevada , Granada, Spain
| | - Belén Feriche
- 1 Department of Physical Education and Sport, Faculty of Sport Sciences, University of Granada , Granada, Spain
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21
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Siebenmann C, Rasmussen P, Sørensen H, Bonne TC, Zaar M, Aachmann-Andersen NJ, Nordsborg NB, Secher NH, Lundby C. Hypoxia increases exercise heart rate despite combined inhibition of β-adrenergic and muscarinic receptors. Am J Physiol Heart Circ Physiol 2015; 308:H1540-6. [DOI: 10.1152/ajpheart.00861.2014] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 04/15/2015] [Indexed: 11/22/2022]
Abstract
Hypoxia increases the heart rate response to exercise, but the mechanism(s) remains unclear. We tested the hypothesis that the tachycardic effect of hypoxia persists during separate, but not combined, inhibition of β-adrenergic and muscarinic receptors. Nine subjects performed incremental exercise to exhaustion in normoxia and hypoxia (fraction of inspired O2 = 12%) after intravenous administration of 1) no drugs (Cont), 2) propranolol (Prop), 3) glycopyrrolate (Glyc), or 4) Prop + Glyc. HR increased with exercise in all drug conditions ( P < 0.001) but was always higher at a given workload in hypoxia than normoxia ( P < 0.001). Averaged over all workloads, the difference between hypoxia and normoxia was 19.8 ± 13.8 beats/min during Cont and similar (17.2 ± 7.7 beats/min, P = 0.95) during Prop but smaller ( P < 0.001) during Glyc and Prop + Glyc (9.8 ± 9.6 and 8.1 ± 7.6 beats/min, respectively). Cardiac output was enhanced by hypoxia ( P < 0.002) to an extent that was similar between Cont, Glyc, and Prop + Glyc (2.3 ± 1.9, 1.7 ± 1.8, and 2.3 ± 1.2 l/min, respectively, P > 0.4) but larger during Prop (3.4 ± 1.6 l/min, P = 0.004). Our results demonstrate that the tachycardic effect of hypoxia during exercise partially relies on vagal withdrawal. Conversely, sympathoexcitation either does not contribute or increases heart rate through mechanisms other than β-adrenergic transmission. A potential candidate is α-adrenergic transmission, which could also explain why a tachycardic effect of hypoxia persists during combined β-adrenergic and muscarinic receptor inhibition.
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Affiliation(s)
- C. Siebenmann
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zurich, Switzerland
- Department of Environmental Physiology, School of Technology and Health, Royal Institute of Technology, Solna, Sweden
| | - P. Rasmussen
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zurich, Switzerland
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - H. Sørensen
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - T. C. Bonne
- Department of Nutrition, Exercise, and Sports, University of Copenhagen, Copenhagen, Denmark; and
| | - M. Zaar
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | | | - N. B. Nordsborg
- Department of Nutrition, Exercise, and Sports, University of Copenhagen, Copenhagen, Denmark; and
| | - N. H. Secher
- Department of Anesthesia, The Copenhagen Muscle Research Centre, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - C. Lundby
- Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zurich, Switzerland
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22
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Affiliation(s)
- James P. Fisher
- School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
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23
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Iwamoto E, Katayama K, Ishida K. Exercise intensity modulates brachial artery retrograde blood flow and shear rate during leg cycling in hypoxia. Physiol Rep 2015; 3:3/6/e12423. [PMID: 26038470 PMCID: PMC4510625 DOI: 10.14814/phy2.12423] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The purpose of this study was to elucidate the effect of exercise intensity on retrograde blood flow and shear rate (SR) in an inactive limb during exercise under normoxic and hypoxic conditions. The subjects performed two maximal exercise tests on a semi-recumbent cycle ergometer to estimate peak oxygen uptake (O2peak) while breathing normoxic (inspired oxygen fraction [FIO2 = 0.21]) and hypoxic (FIO2 = 0.12 or 0.13) gas mixtures. Subjects then performed four exercise bouts at the same relative intensities (30 and 60% O2peak) for 30 min under normoxic or hypoxic conditions. Brachial artery diameter and blood velocity were simultaneously recorded, using Doppler ultrasonography. Retrograde SR was enhanced with increasing exercise intensity under both conditions at 10 min of exercise. Thereafter, retrograde blood flow and SR in normoxia returned to pre-exercise levels, with no significant differences between the two exercise intensities. In contrast, retrograde blood flow and SR in hypoxia remained significantly elevated above baseline and was significantly greater at 60% than at 30% O2peak. We conclude that differences in exercise intensity affect brachial artery retrograde blood flow and SR during prolonged exercise under hypoxic conditions.
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Affiliation(s)
- Erika Iwamoto
- School of Health Sciences, Sapporo Medical University, Sapporo, Japan
| | - Keisho Katayama
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Koji Ishida
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan Graduate School of Medicine, Nagoya University, Nagoya, Japan
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24
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Katayama K, Itoh Y, Saito M, Koike T, Ishida K. Sympathetic vasomotor outflow and blood pressure increase during exercise with expiratory resistance. Physiol Rep 2015; 3:3/5/e12421. [PMID: 26019293 PMCID: PMC4463841 DOI: 10.14814/phy2.12421] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The purpose of the present study was to elucidate the effect of increasing expiratory muscle work on sympathetic vasoconstrictor outflow and arterial blood pressure (BP) during dynamic exercise. We hypothesized that expiratory muscle fatigue would elicit increases in sympathetic vasomotor outflow and BP during submaximal exercise. The subjects performed four submaximal exercise tests; two were maximal expiratory pressure (PEmax) tests and two were muscle sympathetic nerve activity (MSNA) tests. In each test, the subjects performed two 10-min exercises at 40% peak oxygen uptake using a cycle ergometer in a semirecumbent position [spontaneous breathing for 5 min and voluntary hyperpnoea with and without expiratory resistive breathing for 5 min (breathing frequency: 60 breaths/min, inspiratory and expiratory times were set at 0.5 sec)]. PEmax was estimated before and immediately after exercises. MSNA was recorded via microneurography of the right median nerve at the elbow. PEmax decreased following exercise with expiratory resistive breathing, while no change was found without resistance. A progressive increase in MSNA burst frequency (BF) appeared during exercise with expiratory resistance (MSNA BF, without resistance: +22 ± 5%, with resistance: +44 ± 8%, P < 0.05), accompanied by an augmentation of BP (mean BP, without resistance: +5 ± 2%, with resistance: +29 ± 5%, P < 0.05). These results suggest that an enhancement of expiratory muscle activity leads to increases in sympathetic vasomotor outflow and BP during dynamic leg exercise.
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Affiliation(s)
- Keisho Katayama
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Yuka Itoh
- Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Mitsuru Saito
- Faculty of Psychological and Physical Science, Aichigakuin University, Nisshin, Japan
| | - Teruhiko Koike
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan Graduate School of Medicine, Nagoya University, Nagoya, Japan
| | - Koji Ishida
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan Graduate School of Medicine, Nagoya University, Nagoya, Japan
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25
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Adeoye OO, Silpanisong J, Williams JM, Pearce WJ. Role of the sympathetic autonomic nervous system in hypoxic remodeling of the fetal cerebral vasculature. J Cardiovasc Pharmacol 2015; 65:308-16. [PMID: 25853949 PMCID: PMC4391294 DOI: 10.1097/fjc.0000000000000192] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Fetal hypoxia triggers compensatory angiogenesis and remodeling through mechanisms not fully elucidated. In response to hypoxia, hypoxia-inducible factor drives expression of cytokines that exert multiple effects on cerebral structures. Among these, the artery wall is composed of a heterogeneous cell mix and exhibits distinct patterns of cellular differentiation and reactivity. Governing these patterns are the vascular endothelium, smooth muscle (SM), adventitia, sympathetic perivascular nerves (SPN), and the parenchyma. Although an extensive literature details effects of nonneuronal factors on cerebral arteries, the trophic role of perivascular nerves remains unclear. Hypoxia increases sympathetic innervation with subsequent release of norepinephrine (NE), neuropeptide-Y (NPY), and adenosine triphosphate, which exert motor and trophic effects on cerebral arteries and influence dynamic transitions among SM phenotypes. Our data also suggest that the cerebrovasculature reacts very differently to hypoxia in fetuses and adults, and we hypothesize that these differences arise from age-related differences in arterial SM phenotype reactivity and proximity to trophic factors, particularly of neural origin. We provide an integration of recent literature focused on mechanisms by which SPN mediate hypoxic remodeling. Our recent findings suggest that trophic effects of SPN on cerebral arteries accelerate functional maturation through shifts in SM phenotype in an age-dependent manner.
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MESH Headings
- Adenosine Triphosphate/metabolism
- Adult
- Age Factors
- Animals
- Cerebrovascular Circulation
- Fetal Hypoxia/complications
- Fetal Hypoxia/metabolism
- Fetal Hypoxia/physiopathology
- Humans
- Hypoxia, Brain/complications
- Hypoxia, Brain/metabolism
- Hypoxia, Brain/physiopathology
- Muscle, Smooth, Vascular/innervation
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/pathology
- Muscle, Smooth, Vascular/physiopathology
- Neovascularization, Pathologic/etiology
- Neovascularization, Pathologic/metabolism
- Neovascularization, Pathologic/physiopathology
- Neuropeptide Y/metabolism
- Norepinephrine/metabolism
- Sympathetic Nervous System/metabolism
- Sympathetic Nervous System/physiopathology
- Vascular Remodeling
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Affiliation(s)
- Olayemi O Adeoye
- Divisions of Physiology, Pharmacology, and Biochemistry, Center for Perinatal Biology, Loma Linda University School of Medicine, Loma Linda, CA
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26
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Notarius CF, Millar PJ, Murai H, Morris BL, Marzolini S, Oh P, Floras JS. Divergent muscle sympathetic responses to dynamic leg exercise in heart failure and age-matched healthy subjects. J Physiol 2014; 593:715-22. [PMID: 25398528 DOI: 10.1113/jphysiol.2014.281873] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 11/03/2014] [Indexed: 01/12/2023] Open
Abstract
KEY POINTS People with diminished ventricular contraction who develop heart failure have higher sympathetic nerve firing rates at rest compared with healthy individuals of a similar age and this is associated with less exercise capacity. During handgrip exercise, sympathetic nerve activity to muscle is higher in patients with heart failure but the response to leg exercise is unknown because its recording requires stillness. We measured sympathetic activity from one leg while the other leg cycled at a moderate level and observed a decrease in nerve firing rate in healthy subjects but an increase in subjects with heart failure. Because these nerves release noradrenaline, which can restrict muscle blood flow, this observation helps explain the limited exercise capacity of patients with heart failure. Lower nerve traffic during exercise was associated with greater peak oxygen uptake, suggesting that if exercise training attenuated sympathetic outflow functional capacity in heart failure would improve. ABSTRACT The reflex fibular muscle sympathetic nerve (MSNA) response to dynamic handgrip exercise is elicited at a lower threshold in heart failure with reduced ejection fraction (HFrEF). The present aim was to test the hypothesis that the contralateral MSNA response to mild to moderate dynamic one-legged exercise is augmented in HFrEF relative to age- and sex-matched controls. Heart rate (HR), blood pressure and MSNA were recorded in 16 patients with HFrEF (left ventricular ejection fraction = 31 ± 2%; age 62 ± 3 years, mean ± SE) and 13 healthy control subjects (56 ± 2 years) before and during 2 min of upright one-legged unloaded cycling followed by 2 min at 50% of peak oxygen uptake (V̇O2,peak). Resting HR and blood pressure were similar between groups whereas MSNA burst frequency was higher (50.0 ± 2.0 vs. 42.3 ± 2.7 bursts min(-1), P = 0.03) and V̇O2,peak lower (18.0 ± 2.0 vs. 32.6 ± 2.8 ml kg(-1) min(-1), P < 0.001) in HFrEF. Exercise increased HR (P < 0.001) with no group difference (P = 0.1). MSNA burst frequency decreased during mild to moderate dynamic exercise in the healthy controls but increased in HFrEF (-5.5 ± 2.0 vs. 6.9 ± 1.8 bursts min(-1), P < 0.001). Exercise capacity correlated inversely with MSNA burst frequency at 50% V̇O2,peak (n = 29; r = -0.64; P < 0.001). At the same relative workload, one-legged dynamic exercise elicited a fall in MSNA burst frequency in healthy subjects but sympathoexcitation in HFrEF, a divergence probably reflecting between-group differences in reflexes engaged by cycling. This finding, coupled with an inverse relationship between MSNA burst frequency during loaded cycling and subjects' V̇O2,peak, is consistent with a neurogenic determinant of exercise capacity in HFrEF.
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Affiliation(s)
- Catherine F Notarius
- University Health Network and Mount Sinai Hospital Division of Cardiology, University of Toronto, Toronto, Ontario, Canada
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27
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Katayama K, Yamashita S, Iwamoto E, Ishida K. Flow-mediated dilation in the inactive limb following acute hypoxic exercise. Clin Physiol Funct Imaging 2014; 36:60-9. [DOI: 10.1111/cpf.12194] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 09/01/2014] [Indexed: 01/24/2023]
Affiliation(s)
- Keisho Katayama
- Research Center of Health; Physical Fitness and Sports; Nagoya University; Nagoya Japan
| | - Shin Yamashita
- Graduate School of Education and Human Development; Nagoya University; Nagoya Japan
| | - Erika Iwamoto
- School of Health Sciences; Sapporo Medical University; Sapporo Japan
| | - Koji Ishida
- Research Center of Health; Physical Fitness and Sports; Nagoya University; Nagoya Japan
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28
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Katayama K, Ishida K, Saito M, Koike T, Hirasawa A, Ogoh S. Enhanced muscle pump during mild dynamic leg exercise inhibits sympathetic vasomotor outflow. Physiol Rep 2014; 2:2/7/e12070. [PMID: 25347854 PMCID: PMC4187562 DOI: 10.14814/phy2.12070] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Muscle sympathetic nerve activity (MSNA) is not increased during leg cycling at light and mild intensities, despite activation of central command and the exercise pressor reflex. We determined whether increasing central blood volume and loading the cardiopulmonary baroreceptors modulate sympathetic vasomotor outflow during leg cycling. To this end, we changed the pedaling frequency to enhance skeletal muscle pump. Subjects performed two leg cycle exercises at differential pedal rates of 60 and 80 rpm (60EX and 80EX trials) for two conditions (with and without MSNA measurement). In each trial, subjects completed leg cycling with a differential workload to maintain constant oxygen consumption (VO2). MSNA was recorded via microneurography at the right median nerve of the elbow. Without MSNA measurement, thoracic impedance, stroke volume (SV), and cardiac output (CO) were measured non‐invasively using impedance cardiography. Heart rate and VO2 during exercise did not differ between the 60EX and 80EX trials. Changes in thoracic impedance, SV, and CO during the 80EX trial were greater than during the 60EX trial. MSNA during the 60EX trial was unchanged compared with that at rest (25.8 ± 3.1 [rest] to 28.3 ± 3.4 [exercise] bursts/min), whereas a significant decrease in MSNA was observed during the 80EX trial (25.8 ± 2.8 [rest] to 19.7 ± 2.0 [exercise] bursts/min). These results suggest that a muscle pump‐induced increase in central blood volume, and thereby loading of cardiopulmonary baroreceptors, could inhibit sympathetic vasomotor outflow during mild dynamic leg exercise, despite activation of central command and the exercise pressor reflex. Muscle sympathetic nerve activity during leg cycling was reduced when central blood volume was manipulated by increasing the pedaling frequency. This result suggest that sympathetic vasomotor outflow is strongly affected by loading of cardiopulmonary baroreceptors at light and mild dynamic leg exercise to maintain arterial blood pressure.
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Affiliation(s)
- Keisho Katayama
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan
| | - Koji Ishida
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan
| | - Mitsuru Saito
- Faculty of Psychological and Physical Science, Aichigakuin University, Nisshin, Japan
| | - Teruhiko Koike
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan
| | - Ai Hirasawa
- Department of Biomedical Engineering, Toyo University, Kawagoe, Japan
| | - Shigehiko Ogoh
- Department of Biomedical Engineering, Toyo University, Kawagoe, Japan
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29
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Edgell H, Stickland MK. Activation of the carotid chemoreflex secondary to muscle metaboreflex stimulation in men. Am J Physiol Regul Integr Comp Physiol 2014; 306:R693-700. [PMID: 24573180 DOI: 10.1152/ajpregu.00472.2013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recent work has shown that the carotid chemoreceptor (CC) contributes to sympathetic control of cardiovascular function during exercise, despite no evidence of increased circulating CC stimuli, suggesting enhanced CC activity/sensitivity. As interactions between metaboreceptors and chemoreceptors have been previously observed, the purpose of this study was to isolate the metaboreflex while acutely stimulating or inhibiting the CC to determine whether the metaboreflex increased CC activity/sensitivity. Fourteen young healthy men (height: 177.0 ± 2.1 cm, weight: 85.8 ± 5.5 kg, age: 24.6 ± 1.1 yr) performed three trials of 40% maximal voluntary contraction handgrip for 2 min, followed by 3 min of postexercise circulatory occlusion (PECO) to stimulate the metaboreflex. In random order, subjects either breathed room air, hypoxia (target SPo2 = 85%), or hyperoxia (FiO2 = 1.0) during the PECO to modulate the chemoreflex. After these trials, a resting hypoxia trial was conducted without handgrip or PECO. Ventilation (Ve), heart rate (HR), blood pressure, and muscle sympathetic nervous activity (MSNA) data were continuously obtained. Relative to normoxic PECO, inhibition of the CC during hyperoxic PECO resulted in lower MSNA (P = 0.038) and HR (P = 0.021). Relative to normoxic PECO, stimulation of the CC during hypoxic PECO resulted in higher HR (P < 0.001) and Ve (P < 0.001). The ventilatory and MSNA responses to hypoxic PECO were not greater than the sum of the responses to hypoxia and PECO individually, indicating that the CC are not sensitized during metaboreflex activation. These results demonstrate that stimulation of the metaboreflex activates, but does not sensitize the CC, and help explain the enhanced CC activity with exercise.
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Affiliation(s)
- H Edgell
- Pulmonary Division, Department of Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada
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30
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Iwamoto E, Katayama K, Yamashita S, Oshida Y, Ishida K. Retrograde blood flow in the inactive limb is enhanced during constant-load leg cycling in hypoxia. Eur J Appl Physiol 2013; 113:2565-75. [PMID: 23864526 DOI: 10.1007/s00421-013-2694-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2013] [Accepted: 07/04/2013] [Indexed: 11/30/2022]
Abstract
PURPOSE This study aimed to elucidate the effects of hypoxia on the pattern of oscillatory blood flow in the inactive limb during constant-load dynamic exercise. We hypothesised that retrograde blood flow in the brachial artery of the inactive limb would increase during constant-load leg cycling under hypoxic conditions. METHODS Three maximal exercise tests were conducted in eight healthy males on a semi-recumbent cycle ergometer while the subjects breathed a normoxic [inspired oxygen fraction (FIO2) = 0.209] or two hypoxic gas mixtures (FIO2 = 0.155 and 0.120). Subjects then performed submaximal exercise at the same relative exercise intensity of 60 % peak oxygen uptake under normoxic or the two hypoxic conditions for 30 min. Brachial artery blood velocity and diameter were recorded simultaneously during submaximal exercise using Doppler ultrasonography. RESULTS Antegrade blood flow gradually increased during exercise, with no significant differences among the three trials. Retrograde blood flow showed a biphasic response, with an initial increase followed by a gradual decrease during normoxic exercise. In contrast, retrograde blood flow significantly increased during moderate and severe hypoxic exercise, and remained elevated above normoxic conditions during exercise. At 30 min of exercise, the magnitude of the change in retrograde blood flow during exercise was greater as the level of hypoxia increased (normoxia: -18.7 ± 23.5 ml min(-1); moderate hypoxia: -39.3 ± 21.4 ml min(-1); severe hypoxia: -64.0 ± 36.3 ml min(-1)). CONCLUSION These results indicate that moderate and severe hypoxia augment retrograde blood flow in the inactive limb during constant-load dynamic leg exercise.
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Affiliation(s)
- Erika Iwamoto
- Second Division of Physical Therapy, Department of Physical Therapy, School of Health Sciences, Sapporo Medical University, South1, West17, Chuo-ku, Sapporo, 060-8556, Japan,
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31
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Lador F, Tam E, Adami A, Kenfack MA, Bringard A, Cautero M, Moia C, Morel DR, Capelli C, Ferretti G. Cardiac output, O2 delivery and kinetics during step exercise in acute normobaric hypoxia. Respir Physiol Neurobiol 2013; 186:206-13. [DOI: 10.1016/j.resp.2013.01.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 01/28/2013] [Accepted: 01/30/2013] [Indexed: 11/28/2022]
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32
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Katayama K, Yamashita S, Ishida K, Iwamoto E, Koike T, Saito M. Hypoxic effects on sympathetic vasomotor outflow and blood pressure during exercise with inspiratory resistance. Am J Physiol Regul Integr Comp Physiol 2013; 304:R374-82. [DOI: 10.1152/ajpregu.00489.2012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of the present study was to clarify the influence of inspiratory resistive breathing during exercise under hypoxic conditions on muscle sympathetic nerve activity (MSNA) and blood pressure (BP). Six healthy males completed this study. The subjects performed a submaximal exercise test using a cycle ergometer in a semirecumbent position under normoxic [inspired oxygen fraction (FiO2) = 0.21] and hypoxic (FiO2 = 0.12–0.13) conditions. The subjects carried out two 10-min exercises at 40% peak oxygen uptake [spontaneous breathing for 5 min and voluntary breathing with inspiratory resistance for 5 min (breathing frequency: 60 breaths/min, inspiratory and expiratory times were set at 0.5 s each)]. MSNA was recorded via microneurography of the right median nerve at the elbow. A progressive increase in MSNA burst frequency (BF) during leg-cycling exercise with inspiratory resistance in normoxia and hypoxia were accompanied by an augmentation of BP. The increased MSNA BF and mean arterial BP (MBP) during exercise with inspiratory resistive breathing in hypoxia (MSNA BF, 55.7 ± 1.4 bursts/min, MBP, 134.3 ± 6.6 mmHg) were higher than those in normoxia (MSNA BF, 39.2 ± 1.8 bursts/min, MBP, 123.6 ± 4.5 mmHg). These results suggest that an enhancement of inspiratory muscle activity under hypoxic condition leads to large increases in muscle sympathetic vasomotor outflow and BP during dynamic leg exercise.
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Affiliation(s)
- Keisho Katayama
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan
| | - Shin Yamashita
- Graduate School of Education and Human Development, Nagoya University, Nagoya, Japan
| | - Koji Ishida
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan
| | - Erika Iwamoto
- Graduate School of Medicine, Nagoya University, Nagoya, Japan
- School of Health Sciences, Sapporo Medical University, Sapporo, Japan; and
| | - Teruhiko Koike
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan
| | - Mitsuru Saito
- Faculty of Psychological and Physical Science, Aichigakuin University, Nisshin, Japan
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Katayama K, Fujita O, Iemitsu M, Kawano H, Iwamoto E, Saito M, Ishida K. The effect of acute exercise in hypoxia on flow-mediated vasodilation. Eur J Appl Physiol 2012; 113:349-57. [DOI: 10.1007/s00421-012-2442-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 06/07/2012] [Indexed: 10/27/2022]
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IWAMOTO ERIKA, KATAYAMA KEISHO, OSHIDA YOSHIHARU, ISHIDA KOJI. Hypoxia Augments Oscillatory Blood Flow in Brachial Artery during Leg Cycling. Med Sci Sports Exerc 2012; 44:1035-42. [DOI: 10.1249/mss.0b013e31824294f9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Katayama K, Iwamoto E, Ishida K, Koike T, Saito M. Inspiratory muscle fatigue increases sympathetic vasomotor outflow and blood pressure during submaximal exercise. Am J Physiol Regul Integr Comp Physiol 2012; 302:R1167-75. [PMID: 22461178 DOI: 10.1152/ajpregu.00006.2012] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The purpose of this study was to elucidate the influence of inspiratory muscle fatigue on muscle sympathetic nerve activity (MSNA) and blood pressure (BP) response during submaximal exercise. We hypothesized that inspiratory muscle fatigue would elicit increases in sympathetic vasoconstrictor outflow and BP during dynamic leg exercise. The subjects carried out four submaximal exercise tests: two were maximal inspiratory pressure (PI(max)) tests and two were MSNA tests. In the PI(max) tests, the subjects performed two 10-min exercises at 40% peak oxygen uptake using a cycle ergometer in a semirecumbent position [spontaneous breathing for 5 min and with or without inspiratory resistive breathing for 5 min (breathing frequency: 60 breaths/min, inspiratory and expiratory times were each set at 0.5 s)]. Before and immediately after exercise, PI(max) was estimated. In MSNA tests, the subjects performed two 15-min exercises (spontaneous breathing for 5 min, with or without inspiratory resistive breathing for 5 min, and spontaneous breathing for 5 min). MSNA was recorded via microneurography of the right median nerve at the elbow. PI(max) decreased following exercise with resistive breathing, whereas no change was found without resistance. The time-dependent increase in MSNA burst frequency (BF) appeared during exercise with inspiratory resistive breathing, accompanied by an augmentation of diastolic BP (DBP) (with resistance: MSNA, BF +83.4%; DBP, +23.8%; without resistance: MSNA BF, +19.2%; DBP, -0.4%, from spontaneous breathing during exercise). These results suggest that inspiratory muscle fatigue induces increases in muscle sympathetic vasomotor outflow and BP during dynamic leg exercise at mild intensity.
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Affiliation(s)
- Keisho Katayama
- Research Center of Health, Physical Fitness and Sports, Nagoya University, Nagoya, Japan.
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Casey DP, Joyner MJ. Local control of skeletal muscle blood flow during exercise: influence of available oxygen. J Appl Physiol (1985) 2011; 111:1527-38. [PMID: 21885800 DOI: 10.1152/japplphysiol.00895.2011] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Reductions in oxygen availability (O(2)) by either reduced arterial O(2) content or reduced perfusion pressure can have profound influences on the circulation, including vasodilation in skeletal muscle vascular beds. The purpose of this review is to put into context the present evidence regarding mechanisms responsible for the local control of blood flow during acute systemic hypoxia and/or local hypoperfusion in contracting muscle. The combination of submaximal exercise and hypoxia produces a "compensatory" vasodilation and augmented blood flow in contracting muscles relative to the same level of exercise under normoxic conditions. A similar compensatory vasodilation is observed in response to local reductions in oxygen availability (i.e., hypoperfusion) during normoxic exercise. Available evidence suggests that nitric oxide (NO) contributes to the compensatory dilator response under each of these conditions, whereas adenosine appears to only play a role during hypoperfusion. During systemic hypoxia the NO-mediated component of the compensatory vasodilation is regulated through a β-adrenergic receptor mechanism at low-intensity exercise, while an additional (not yet identified) source of NO is likely to be engaged as exercise intensity increases during hypoxia. Potential candidates for stimulating and/or interacting with NO at higher exercise intensities include prostaglandins and/or ATP. Conversely, prostaglandins do not appear to play a role in the compensatory vasodilation during exercise with hypoperfusion. Taken together, the data for both hypoxia and hypoperfusion suggest NO is important in the compensatory vasodilation seen when oxygen availability is limited. This is important from a basic biological perspective and also has pathophysiological implications for diseases associated with either hypoxia or hypoperfusion.
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Affiliation(s)
- Darren P Casey
- Dept. of Anesthesiology, Mayo Clinic, Rochester, MN 55905, USA.
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