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Mallet RT, Burtscher J, Pialoux V, Pasha Q, Ahmad Y, Millet GP, Burtscher M. Molecular Mechanisms of High-Altitude Acclimatization. Int J Mol Sci 2023; 24:ijms24021698. [PMID: 36675214 PMCID: PMC9866500 DOI: 10.3390/ijms24021698] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 01/11/2023] [Accepted: 01/13/2023] [Indexed: 01/17/2023] Open
Abstract
High-altitude illnesses (HAIs) result from acute exposure to high altitude/hypoxia. Numerous molecular mechanisms affect appropriate acclimatization to hypobaric and/or normobaric hypoxia and curtail the development of HAIs. The understanding of these mechanisms is essential to optimize hypoxic acclimatization for efficient prophylaxis and treatment of HAIs. This review aims to link outcomes of molecular mechanisms to either adverse effects of acute high-altitude/hypoxia exposure or the developing tolerance with acclimatization. After summarizing systemic physiological responses to acute high-altitude exposure, the associated acclimatization, and the epidemiology and pathophysiology of various HAIs, the article focuses on molecular adjustments and maladjustments during acute exposure and acclimatization to high altitude/hypoxia. Pivotal modifying mechanisms include molecular responses orchestrated by transcription factors, most notably hypoxia inducible factors, and reciprocal effects on mitochondrial functions and REDOX homeostasis. In addition, discussed are genetic factors and the resultant proteomic profiles determining these hypoxia-modifying mechanisms culminating in successful high-altitude acclimatization. Lastly, the article discusses practical considerations related to the molecular aspects of acclimatization and altitude training strategies.
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Affiliation(s)
- Robert T. Mallet
- Department of Physiology and Anatomy, University of North Texas Health Science Center, Fort Worth, TX 76107, USA
| | - Johannes Burtscher
- Department of Biomedical Sciences, University of Lausanne, CH-1005 Lausanne, Switzerland
- Institute of Sport Sciences, University of Lausanne, CH-1005 Lausanne, Switzerland
| | - Vincent Pialoux
- Inter-University Laboratory of Human Movement Biology EA7424, University Claude Bernard Lyon 1, University of Lyon, FR-69008 Lyon, France
| | - Qadar Pasha
- Institute of Hypoxia Research, New Delhi 110067, India
| | - Yasmin Ahmad
- Defense Institute of Physiology & Allied Sciences (DIPAS), Defense Research & Development Organization(DRDO), New Delhi 110054, India
| | - Grégoire P. Millet
- Department of Biomedical Sciences, University of Lausanne, CH-1005 Lausanne, Switzerland
- Institute of Sport Sciences, University of Lausanne, CH-1005 Lausanne, Switzerland
| | - Martin Burtscher
- Department of Sport Science, University of Innsbruck, A-6020 Innsbruck, Austria
- Austrian Society for Alpine and High-Altitude Medicine, A-6020 Innsbruck, Austria
- Correspondence:
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Park HY, Jung WS, Kim SW, Kim J, Lim K. Effects of Interval Training Under Hypoxia on Hematological Parameters, Hemodynamic Function, and Endurance Exercise Performance in Amateur Female Runners in Korea. Front Physiol 2022; 13:919008. [PMID: 35665230 PMCID: PMC9158122 DOI: 10.3389/fphys.2022.919008] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 05/04/2022] [Indexed: 11/21/2022] Open
Abstract
Interval training under hypoxia (IHT) is commonly used to enhance endurance exercise performance. However, previous studies examining hematologic changes related to the immune system that affect health and conditioning are lacking. This study aimed to evaluate the effects of IHT for 6-weeks on hematological parameters, hemodynamic function, and endurance exercise performance in amateur Korean female runners. Twenty healthy amateur Korean female runners (age: 24.85 ± 3.84 years) were equally assigned to normoxic training group (NTG) for interval training under normoxia (760 mmHg) and hypoxic training group (HTG) for interval training under hypobaric hypoxia (526 mmHg, 3000 m simulated altitude) according to their body composition and endurance exercise performance. All participants performed 120-min of training sessions, consisting of 20-min of warm-up, 60-min of interval training, and 20-min of cool-down. The training program was performed 3-days per week for 6-weeks. Warm-up and cool-down were performed for 20-min at 60% maximal heart rate (HRmax). The interval training sessions comprised 10 repetitions of interval exercise (5-min of exercise corresponding to 90–95% HRmax and 1-min of rest) on a treadmill. All participants underwent measurements of hematological parameters, hemodynamic function, and endurance exercise performance before and after training. Both groups showed a significant increase in erythropoietin (EPO) level and a decrease in monocyte abundance, with EPO showing a greater increase in the HTG than in the NTG. B cell abundance significantly increased in the NTG; hematocrit and neutrophil counts significantly increased, and lymphocyte counts significantly decreased in the HTG. The HTG showed a significant improvement in oxygen uptake, stroke volume index, and end-diastolic volume index compared to the NTG. In addition, both groups showed significant improvements in heart rate, end-systolic volume index, and cardiac output index. The maximal oxygen uptake and 3000 m time trial record were significantly improved in both groups, and the HTG showed a tendency to improve more than the NTG. In conclusion, the IHT was effective in enhancing endurance exercise performance through improved hemodynamic function. Furthermore, hematological parameters of immune system showed a normal range before and after training and were not negatively affected.
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Affiliation(s)
- Hun-Young Park
- Department of Sports Medicine and Science, Graduate School, Konkuk University, Seoul, South Korea
- Physical Activity and Performance Institute (PAPI), Konkuk University, Seoul, South Korea
| | - Won-Sang Jung
- Department of Sports Medicine and Science, Graduate School, Konkuk University, Seoul, South Korea
- Physical Activity and Performance Institute (PAPI), Konkuk University, Seoul, South Korea
| | - Sung-Woo Kim
- Department of Sports Medicine and Science, Graduate School, Konkuk University, Seoul, South Korea
- Physical Activity and Performance Institute (PAPI), Konkuk University, Seoul, South Korea
| | - Jisu Kim
- Department of Sports Medicine and Science, Graduate School, Konkuk University, Seoul, South Korea
- Physical Activity and Performance Institute (PAPI), Konkuk University, Seoul, South Korea
| | - Kiwon Lim
- Department of Sports Medicine and Science, Graduate School, Konkuk University, Seoul, South Korea
- Physical Activity and Performance Institute (PAPI), Konkuk University, Seoul, South Korea
- Department of Physical Education, Konkuk University, Seoul, South Korea
- *Correspondence: Kiwon Lim,
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Debevec T, Millet GP, Brocherie F. Do twelve normobaric hypoxic exposures indeed provoke relevant acclimatization for high-altitude workers? INTERNATIONAL JOURNAL OF BIOMETEOROLOGY 2021; 65:637-638. [PMID: 33175214 DOI: 10.1007/s00484-020-02049-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 10/15/2020] [Accepted: 11/04/2020] [Indexed: 06/11/2023]
Affiliation(s)
- Tadej Debevec
- Faculty of Sport, University of Ljubljana, Ljubljana, Slovenia.
- Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia.
| | - Grégoire P Millet
- Institute of Sport Sciences, University of Lausanne, Lausanne, Switzerland
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Ambroży T, Maciejczyk M, Klimek AT, Wiecha S, Stanula A, Snopkowski P, Pałka T, Jaworski J, Ambroży D, Rydzik Ł, Cynarski W. The Effects of Intermittent Hypoxic Training on Anaerobic and Aerobic Power in Boxers. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:E9361. [PMID: 33327551 PMCID: PMC7765038 DOI: 10.3390/ijerph17249361] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 12/13/2020] [Accepted: 12/14/2020] [Indexed: 02/06/2023]
Abstract
BACKGROUND The aim of the study was to evaluate the effects of intermittent hypoxic training (IHT) on anaerobic and aerobic fitness in elite, national boxers. METHODS The study was conducted over a period of 6 weeks. It comprised 30 national championship boxers, divided into 2 groups: the experimental and control. Both groups performed the same boxing training twice a day (morning and afternoon training). In the afternoon, the experimental group performed training under normobaric conditions in a hypoxic chamber (IHT), while the control group undertook exercise in standard normoxic conditions. In both groups, before and after the 6-week programme, basic anthropometric indices as well as anaerobic (Wingate Test) and aerobic (graded test) fitness were assessed. RESULTS There was a significant increase in anaerobic peak power (988.2 vs. 1011.8 W), mean anaerobic power (741.1 vs. 764.8 W), total work (22.84 vs. 22.39 kJ), and a decrease in fatigue index (20.33 vs. 18.6 W·s-1) as well as time to peak power (5.01 vs. 4.72 s). Such changes were not observed in the control group. In both groups, no significant changes in endurance performance were noted after the training session - peak oxygen uptake did not significantly vary after IHT. CONCLUSIONS Our results have practical application for coaches, as the IHT seems to be effective in improving anaerobic performance among boxers.
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Affiliation(s)
- Tadeusz Ambroży
- Institute of Sports Sciences, University of Physical Education, 31-571 Kraków, Poland; (T.A.); (J.J.); (D.A.)
| | - Marcin Maciejczyk
- Department of Physiology and Biochemistry, Faculty of Physical Education and Sport, University of Physical Education in Kraków, 31-571 Kraków, Poland; (M.M.); (A.T.K.); (T.P.)
| | - Andrzej T. Klimek
- Department of Physiology and Biochemistry, Faculty of Physical Education and Sport, University of Physical Education in Kraków, 31-571 Kraków, Poland; (M.M.); (A.T.K.); (T.P.)
| | - Szczepan Wiecha
- Department of Rehabilitation, Faculty of Physical Education and Sport in Biała Podlaska, Józef Piłsudski University of Physical Education, 00-809 Warsaw, Poland;
| | - Arkadiusz Stanula
- Institute of Sport Science, The Jerzy Kukuczka Academy of Physical Education, Mikołowska 72A, 40-065 Katowice, Poland;
| | - Piotr Snopkowski
- Doctoral School, University of Physical Education in Kraków, 31-571 Kraków, Poland;
| | - Tomasz Pałka
- Department of Physiology and Biochemistry, Faculty of Physical Education and Sport, University of Physical Education in Kraków, 31-571 Kraków, Poland; (M.M.); (A.T.K.); (T.P.)
| | - Janusz Jaworski
- Institute of Sports Sciences, University of Physical Education, 31-571 Kraków, Poland; (T.A.); (J.J.); (D.A.)
| | - Dorota Ambroży
- Institute of Sports Sciences, University of Physical Education, 31-571 Kraków, Poland; (T.A.); (J.J.); (D.A.)
| | - Łukasz Rydzik
- Institute of Sports Sciences, University of Physical Education, 31-571 Kraków, Poland; (T.A.); (J.J.); (D.A.)
| | - Wojciech Cynarski
- Institute of Physical Culture Studies, College of Medical Sciences, University of Rzeszów, 35-310 Rzeszów, Poland;
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Salgado RM, Caldwell AR, Coffman KE, Cheuvront SN, Kenefick RW. Endurance test selection optimized via sample size predictions. J Appl Physiol (1985) 2020; 129:467-473. [PMID: 32730177 DOI: 10.1152/japplphysiol.00408.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Selecting the most appropriate performance test is critical in detecting the effect of an intervention. In this investigation we 1) used time-trial (TT) performance data to estimate sample size requirements for test selection and 2) demonstrated the differences in statistical power between a repeated-measures ANOVA (RM-ANOVA) and analysis of covariance (ANCOVA) for detecting an effect in parallel group design. A retrospective analysis of six altitude studies was completed, totaling 105 volunteers. We quantified the test-retest reliability [i.e., intraclass correlation coefficient (ICC) and standard error of measurement (SEM)] and then calculated the standardized effect size for a 5-20% change in TT performance. With these outcomes, a power analysis was performed and required sample sizes were compared among performance tests. Relative to TT duration, the 11.2-km run had the lowest between-subject variance, and thus greatest statistical power (i.e., required smallest sample size) to detect a given percent change in performance. However, the 3.2-km run was the most reliable test (ICC: 0.89, SEM: 81 s) and thus better suited to detect the smallest absolute (i.e., seconds) change in performance. When TT durations were similar, a running modality (11.2-km run; ICC: 0.83, SEM: 422 s) was far more reliable than cycling (720-kJ cycle; ICC: 0.77, SEM: 480 s). In all scenarios, the ANCOVA provided greater statistical power than the RM-ANOVA. Our results suggest that running tests (3.2 km and 11.2 km) using ANCOVA analysis provide the greatest likelihood of detecting a significant change in performance response to an intervention, particularly in populations unaccustomed to cycling.NEW & NOTEWORTHY This is the first investigation to utilize time-trial (TT) data from previous studies in simulations to estimate statistical power. We developed an easy-to-use decision aid detailing the required sample size needed to detect a given change in TT performance for the purpose of test selection. Furthermore, our detailed methods can be applied to any scenario in which there is an impact of a stressor and the desire to detect a treatment effect.
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Affiliation(s)
- Roy M Salgado
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Aaron R Caldwell
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Kirsten E Coffman
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Samuel N Cheuvront
- Biophysics and Biomedical Modeling Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Robert W Kenefick
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
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Jung WS, Kim SW, Park HY. Interval Hypoxic Training Enhances Athletic Performance and Does Not Adversely Affect Immune Function in Middle- and Long-Distance Runners. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:ijerph17061934. [PMID: 32188027 PMCID: PMC7143158 DOI: 10.3390/ijerph17061934] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/13/2020] [Accepted: 03/15/2020] [Indexed: 02/07/2023]
Abstract
This study evaluated the effects of intermittent interval training in hypoxic conditions for six weeks compared with normoxic conditions, on hemodynamic function, autonomic nervous system (ANS) function, immune function, and athletic performance in middle- and long-distance runners. Twenty athletes were divided into normoxic training (normoxic training group (NTG); n = 10; residing and training at sea level) and hypoxic training (hypoxic training group (HTG); n = 10; residing at sea level but training in 526-mmHg hypobaric hypoxia) groups. All dependent variables were measured before, and after, training. The training frequency was 90 min, 3 d per week for six weeks. Body composition showed no significant difference between the two groups. However, the HTG showed more significantly improved athletic performance (e.g., maximal oxygen uptake). The hemodynamic function (e.g., oxygen uptake, oxygen pulse, and cardiac output) during submaximal exercise and ANS function (e.g., standard deviation and root mean square of successive differences, high frequency, and low/high frequency) improved more in the HTG. Immune function parameters were stable within the normal range before and after training in both groups. Therefore, hypoxic training was more effective in enhancing athletic performance, and improving hemodynamic and ANS function; further, it did not adversely affect immune function in competitive runners.
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Affiliation(s)
- Won-Sang Jung
- Physical Activity and Performance Institute, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea; (W.-S.J.); (S.-W.K.)
| | - Sung-Woo Kim
- Physical Activity and Performance Institute, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea; (W.-S.J.); (S.-W.K.)
| | - Hun-Young Park
- Physical Activity and Performance Institute, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea; (W.-S.J.); (S.-W.K.)
- Department of Sports Medicine and Science, Graduate School, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 05029, Korea
- Correspondence: ; Tel.: +(82)-2-2049-6035
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Park HY, Jung WS, Kim J, Hwang H, Lim K. Efficacy of intermittent hypoxic training on hemodynamic function and exercise performance in competitive swimmers. J Exerc Nutrition Biochem 2018; 22:32-38. [PMID: 30661329 PMCID: PMC6343766 DOI: 10.20463/jenb.2018.0028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 12/11/2018] [Indexed: 11/22/2022] Open
Abstract
PURPOSE Hemodynamic function is a parameter indicating oxygen delivery and utilization capacity and is an important determinant of exercise performance. The present study aimed to determine whether intermittent hypoxic training (IHT) ameliorates hemodynamic function and exercise performance in competitive swimmers. METHODS Twenty competitive swimmers (10 men, 10 women) volunteered to participate in the study. Participants were divided into the normoxic training (NT) group and the hypoxic training (HT) group and were subjected to training in a simulated altitude of 3000 m. We evaluated hemodynamic function profiles over 30 min of submaximal exercise on a bicycle and exercise performance before and after 6 weeks of training, which involved continuous exercise at 80% maximal heart rate (HRmax) for 30 min and interval exercise at 90% of HRmax measured before training for 30 min (ten rounds comprising 2 min of exercise followed by 1 min of rest each round). RESULTS Significant changes in oxygen consumption (decrease) and end-diastolic volume (increase) were observed only in the HT group. Heart rate (HR), cardiac output (CO), and ejection fraction (EF) were significantly reduced in both groups, but the reduction rates of HR and CO were greater in the HT group than in the NT group. Exercise performance measures, including maximal oxygen consumption and 400-m time trial, were significantly increased only in the HT group. CONCLUSION Our findings suggested that 6 weeks of IHT, which involved high-intensity continuous and interval exercise, can effectively improve exercise performance by enhancing hemodynamic function in competitive swimmers.
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박훈영, 임기원, 김지수. Exercise physiology basis and necessity of hypoxic training to improve exercise performance in elite athletes. ACTA ACUST UNITED AC 2018. [DOI: 10.24985/kjss.2018.29.4.737] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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9
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Burtscher M, Niedermeier M, Burtscher J, Pesta D, Suchy J, Strasser B. Preparation for Endurance Competitions at Altitude: Physiological, Psychological, Dietary and Coaching Aspects. A Narrative Review. Front Physiol 2018; 9:1504. [PMID: 30425646 PMCID: PMC6218926 DOI: 10.3389/fphys.2018.01504] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 10/05/2018] [Indexed: 01/14/2023] Open
Abstract
It was the Summer Olympic Games 1968 held in Mexico City (2,300 m) that required scientists and coaches to cope with the expected decline of performance in endurance athletes and to establish optimal preparation programs for competing at altitude. From that period until now many different recommendations for altitude acclimatization in advance of an altitude competition were proposed, ranging from several hours to several weeks. Those recommendations are mostly based on the separate consideration of the physiology of acclimatization, psychological issues, performance changes, logistical or individual aspects, but there is no review considering all these aspects in their entirety. Therefore, the present work primarily focusses on the period of altitude sojourn prior to the competition at altitude based on physiological and psychological aspects complemented by nutritional and sports practical considerations.
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Affiliation(s)
- Martin Burtscher
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria.,Austrian Society for Alpine and Mountain Medicine, Innsbruck, Austria
| | - Martin Niedermeier
- Department of Sport Science, University of Innsbruck, Innsbruck, Austria
| | - Johannes Burtscher
- Laboratory of Molecular and Chemical Biology of Neurodegeneration, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Dominik Pesta
- Institute for Clinical Diabetology, German Diabetes Center, Leibniz Institute for Diabetes Research at Heinrich Heine University, Düsseldorf, Germany.,German Center for Diabetes Research, München-Neuherberg, Germany
| | - Jiri Suchy
- Faculty of Physical Education and Sport, Charles University, Prague, Czechia
| | - Barbara Strasser
- Department of Epidemiology and Preventive Medicine, University of Regensburg, Regensburg, Germany.,Medical School, Sigmund Freud University, Vienna, Austria
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Twomey R, Wrightson J, Fletcher H, Avraam S, Ross E, Dekerle J. Exercise-induced Fatigue in Severe Hypoxia after an Intermittent Hypoxic Protocol. Med Sci Sports Exerc 2018; 49:2422-2432. [PMID: 28708702 DOI: 10.1249/mss.0000000000001371] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
PURPOSE Exercise-induced central fatigue is alleviated after acclimatization to high altitude. The adaptations underpinning this effect may also be induced with brief, repeated exposures to severe hypoxia. The purpose of this study was to determine whether (i) exercise tolerance in severe hypoxia would be improved after an intermittent hypoxic (IH) protocol and (ii) exercise-induced central fatigue would be alleviated after an IH protocol. METHODS Nineteen recreationally active men were randomized into two groups who completed ten 2-h exposures in severe hypoxia (IH: partial pressure of inspired O2 82 mm Hg; n = 11) or normoxia (control; n = 8). Seven sessions involved cycling for 30 min at 25% peak power (W˙peak) in IH and at a matched heart rate in normoxia. Participants performed baseline constant-power cycling to task failure in severe hypoxia (TTF-Pre). After the intervention, the cycling trial was repeated (TTF-Post). Before and after exercise, responses to transcranial magnetic stimulation and supramaximal femoral nerve stimulation were obtained to assess central and peripheral contributions to neuromuscular fatigue. RESULTS From pre- to postexercise in TTF-Pre, maximal voluntary contraction (MVC), cortical voluntary activation (VATMS), and potentiated twitch force (Qtw,pot) decreased in both groups (all P < 0.05). After IH, TTF-Post was improved (535 ± 213 s vs 713 ± 271 s, P < 0.05) and an additional isotime trial was performed. After the IH intervention only, the reduction in MVC and VATMS was attenuated at isotime (P < 0.05). No differences were observed in the control group. CONCLUSIONS Whole-body exercise tolerance in severe hypoxia was prolonged after a protocol of IH. This may be related to an alleviation of the central contribution to neuromuscular fatigue.
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Affiliation(s)
- Rosie Twomey
- 1Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, CANADA; 2Centre for Sport and Exercise Science and Medicine, University of Brighton, Eastbourne, UNITED KINGDOM; and 3English Institute of Sport, Bisham Abbey National Sports Centre, Marlow, UNITED KINGDOM
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Lee BJ, Miller A, James RS, Thake CD. Cross Acclimation between Heat and Hypoxia: Heat Acclimation Improves Cellular Tolerance and Exercise Performance in Acute Normobaric Hypoxia. Front Physiol 2016; 7:78. [PMID: 27014080 PMCID: PMC4781846 DOI: 10.3389/fphys.2016.00078] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 02/15/2016] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND The potential for cross acclimation between environmental stressors is not well understood. Thus, the aim of this investigation was to determine the effect of fixed-workload heat or hypoxic acclimation on cellular, physiological, and performance responses during post acclimation hypoxic exercise in humans. METHOD Twenty-one males (age 22 ± 5 years; stature 1.76 ± 0.07 m; mass 71.8 ± 7.9 kg; [Formula: see text]O2 peak 51 ± 7 mL(.)kg(-1.)min(-1)) completed a cycling hypoxic stress test (HST) and self-paced 16.1 km time trial (TT) before (HST1, TT1), and after (HST2, TT2) a series of 10 daily 60 min training sessions (50% N [Formula: see text]O2 peak) in control (CON, n = 7; 18°C, 35% RH), hypoxic (HYP, n = 7; fraction of inspired oxygen = 0.14, 18°C, 35% RH), or hot (HOT, n = 7; 40°C, 25% RH) conditions. RESULTS TT performance in hypoxia was improved following both acclimation treatments, HYP (-3:16 ± 3:10 min:s; p = 0.0006) and HOT (-2:02 ± 1:02 min:s; p = 0.005), but unchanged after CON (+0:31 ± 1:42 min:s). Resting monocyte heat shock protein 72 (mHSP72) increased prior to HST2 in HOT (62 ± 46%) and HYP (58 ± 52%), but was unchanged after CON (9 ± 46%), leading to an attenuated mHSP72 response to hypoxic exercise in HOT and HYP HST2 compared to HST1 (p < 0.01). Changes in extracellular hypoxia-inducible factor 1-α followed a similar pattern to those of mHSP72. Physiological strain index (PSI) was attenuated in HOT (HST1 = 4.12 ± 0.58, HST2 = 3.60 ± 0.42; p = 0.007) as a result of a reduced HR (HST1 = 140 ± 14 b.min(-1); HST2 131 ± 9 b.min(-1) p = 0.0006) and Trectal (HST1 = 37.55 ± 0.18°C; HST2 37.45 ± 0.14°C; p = 0.018) during exercise. Whereas PSI did not change in HYP (HST1 = 4.82 ± 0.64, HST2 4.83 ± 0.63). CONCLUSION Heat acclimation improved cellular and systemic physiological tolerance to steady state exercise in moderate hypoxia. Additionally we show, for the first time, that heat acclimation improved cycling time trial performance to a magnitude similar to that achieved by hypoxic acclimation.
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Affiliation(s)
- Ben J Lee
- Department for Health, University of BathBath, UK; Centre for Applied Biological and Exercise Sciences, Coventry UniversityCoventry, UK
| | - Amanda Miller
- Centre for Applied Biological and Exercise Sciences, Coventry University Coventry, UK
| | - Rob S James
- Centre for Applied Biological and Exercise Sciences, Coventry University Coventry, UK
| | - Charles D Thake
- Centre for Applied Biological and Exercise Sciences, Coventry University Coventry, UK
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Shah NM, Hussain S, Cooke M, O’Hara JP, Mellor A. Wilderness medicine at high altitude: recent developments in the field. Open Access J Sports Med 2015; 6:319-28. [PMID: 26445563 PMCID: PMC4590685 DOI: 10.2147/oajsm.s89856] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Travel to high altitude is increasingly popular. With this comes an increased incidence of high-altitude illness and therefore an increased need to improve our strategies to prevent and accurately diagnose these. In this review, we provide a summary of recent advances of relevance to practitioners who may be advising travelers to altitude. Although the Lake Louise Score is now widely used as a diagnostic tool for acute mountain sickness (AMS), increasing evidence questions the validity of doing so, and of considering AMS as a single condition. Biomarkers, such as brain natriuretic peptide, are likely correlating with pulmonary artery systolic pressure, thus potential markers of the development of altitude illness. Established drug treatments include acetazolamide, nifedipine, and dexamethasone. Drugs with a potential to reduce the risk of developing AMS include nitrate supplements, propagators of nitric oxide, and supplemental iron. The role of exercise in the development of altitude illness remains hotly debated, and it appears that the intensity of exercise is more important than the exercise itself. Finally, despite copious studies demonstrating the value of preacclimatization in reducing the risk of altitude illness and improving performance, an optimal protocol to preacclimatize an individual remains elusive.
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Affiliation(s)
- Neeraj M Shah
- Division of Asthma, Allergy and Lung Biology, King’s College London, UK
| | - Sidra Hussain
- School of Medicine, University College London, London, UK
| | - Mark Cooke
- Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, UK
| | - John P O’Hara
- Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, UK
| | - Adrian Mellor
- Research Institute for Sport, Physical Activity and Leisure, Leeds Beckett University, Leeds, UK
- Academic Department of Military Anaesthesia and Critical Care, Royal Centre for Defence Medicine, Birmingham, UK
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13
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McLean BD, Gore CJ, Kemp J. Application of 'live low-train high' for enhancing normoxic exercise performance in team sport athletes. Sports Med 2015; 44:1275-87. [PMID: 24849544 DOI: 10.1007/s40279-014-0204-8] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
BACKGROUND AND OBJECTIVE Hypoxic training techniques are increasingly used by athletes in an attempt to improve performance in normoxic environments. The 'live low-train high (LLTH)' model of hypoxic training may be of particular interest to athletes because LLTH protocols generally involve shorter hypoxic exposures (approximately two to five sessions per week of <3 h) than other traditional hypoxic training techniques (e.g., live high-train high or live high-train low). However, the methods employed in LLTH studies to date vary greatly with respect to exposure times, training intensities, training modalities, degrees of hypoxia and performance outcomes assessed. Whilst recent reviews provide some insight into how LLTH may be applied to enhance performance, little attention has been given to how training intensity/modality may specifically influence subsequent performance in normoxia. Therefore, this systematic review aims to evaluate the normoxic performance outcomes of the available LLTH literature, with a particular focus on training intensity and modality. DATA SOURCES AND STUDY SELECTION A systematic search was conducted to capture all LLTH studies with a matched normoxic (control) training group and the assessment of performance under normoxic conditions. Studies were excluded if no training was completed during the hypoxic exposures, or if these exposures exceeded 3 h per day. Four electronic databases were searched (PubMed, SPORTDiscus, EMBASE and Web of Science) during August 2013, and these searches were supplemented by additional manual searches until December 2013. RESULTS After the electronic and manual searches, 40 papers were deemed to meet the inclusion criteria, representing 31 separate studies. Within these 31 studies, four types of LLTH were identified: (1) continuous low-intensity training in hypoxia (CHT, n = 16), (2) interval hypoxic training (IHT, n = 4), (3) repeated sprint training in hypoxia (RSH, n = 3) and (4) resistance training in hypoxia (RTH, n = 4). Four studies also used a combination of CHT and IHT. The majority of studies reported no difference in normoxic performance between the hypoxic and normoxic training groups (n = 19), while nine reported greater improvements in the hypoxic group and three reported poorer outcomes compared with the control group. Selection of training intensity (including matching relative or absolute intensity between normoxic and hypoxic groups) was identified as a key factor in mediating the subsequent normoxic performance outcomes. Five studies included some form of normoxic training for the hypoxic group and 14 studies assessed performance outcomes not specific to the training intensity/modality completed during the training intervention. CONCLUSION Four modes of LLTH are identified in the current literature (CHT, IHT, RSH and RTH), with training mode and intensity appearing to be key factors in mediating subsequent performance responses in normoxia. Improvements in normoxic performance appear most likely following high-intensity, short-term and intermittent training (e.g., IHT, RSH). LLTH programmes should carefully apply the principles of training and testing specificity and include some high-intensity training in normoxia. For RTH, it is unclear whether the associated adaptations are greater than those of traditional (maximal) resistance training programmes.
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Affiliation(s)
- Blake D McLean
- Sport Science Department, Collingwood Football Club, Melbourne, Australia,
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14
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Robach P, Bonne T, Flück D, Bürgi S, Toigo M, Jacobs RA, Lundby C. Hypoxic training: effect on mitochondrial function and aerobic performance in hypoxia. Med Sci Sports Exerc 2015; 46:1936-45. [PMID: 24674976 DOI: 10.1249/mss.0000000000000321] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
PURPOSE The effects of hypoxic training on exercise performance remain controversial. Here, we tested the hypotheses that i) hypoxic training possesses ergogenic effects at sea level and altitude and ii) the benefits are primarily mediated by improved mitochondrial function of the skeletal muscle. METHODS We determined aerobic performance (incremental test to exhaustion and time trial for a set amount of work) in moderately trained subjects undergoing 6 wk of endurance training (3-4 times per week, 60 min per session) in normoxia (placebo, n = 8) or normobaric hypoxia (FIO2 = 0.15, n = 9) using a double-blind and randomized design. Exercise tests were performed in normoxia and acute hypoxia (FIO2 = 0.15). Skeletal muscle mitochondrial respiratory capacities and electron coupling efficiencies were measured via high-resolution respirometry. Total hemoglobin mass was assessed by carbon monoxide rebreathing. RESULTS Skeletal muscle respiratory capacity was not altered by training or hypoxia; however, electron coupling control respective to fat oxidation slightly diminished with hypoxic training. Hypoxic training did increase total hemoglobin mass more than the placebo (8.4% vs 3.3%, P = 0.02). In normoxia, hypoxic training had no additive effect on maximal measures of oxygen uptake or time trial performance. In acute hypoxia, hypoxic training conferred no advantage on maximal oxygen uptake but tended to enhance time trial performance more than normoxic training (52% vs 32%, P = 0.09). CONCLUSIONS Our data suggest that, in moderately trained subjects, 6 wk of hypoxic training possesses no ergogenic effect at sea level. It is not excluded that hypoxic training might facilitate endurance capacity at moderate altitude; however, this issue is still open and needs to be further examined.
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Affiliation(s)
- Paul Robach
- 1Ecole Nationale des Sports de Montagne, site de l'Ecole Nationale de Ski et d'Alpinisme, Chamonix, FRANCE; 2Department of Exercise and Sport Sciences, University of Copenhagen, Copenhagen, DENMARK; 3Zürich Center for Integrative Human Physiology, University of Zürich, Zürich, SWITZERLAND; 4Institute of Physiology, University of Zürich, Zürich, SWITZERLAND; and 5Exercise Physiology, Institute of Human Movement Sciences, Eidgenössische Technische Hochschule Zürich, Zürich, SWITZERLAND
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15
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Kim CH, Ryan EJ, Seo Y, Peacock C, Gunstad J, Muller MD, Ridgel AL, Glickman EL. Low intensity exercise does not impact cognitive function during exposure to normobaric hypoxia. Physiol Behav 2015; 151:24-8. [PMID: 26160408 DOI: 10.1016/j.physbeh.2015.07.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 06/16/2015] [Accepted: 07/02/2015] [Indexed: 11/30/2022]
Abstract
Exposure to hypoxia is associated with cognitive impairment, mediated by cerebral deoxygenation. This can be problematic for individuals who perform mental tasks at high altitude. Eight healthy men completed two experimental trials consisting of 5h of exposure to normobaric hypoxia (12.5% O2). In one of the experimental trials (Hypoxia) subjects remained resting in a seated position the entire 5h; in the other experimental trial (Hypoxia and Exercise) subjects rested 2h, cycled for 1h at constant wattage (workload equivalent to 50% of altitude adjusted VO2max), then rested the last 2h. Cerebral oxygenation was measured continuously via near-infrared spectroscopy and cognitive performance was assessed by Trail Making Test A and B. Cerebral oxygenation and cognitive performance both were impaired during exposure to hypoxia. In the Hypoxia and Exercise trial, subjects experienced further declinations in cerebral oxygenation without concomitant decreases in cognitive function. These data demonstrate that cognitive function declines during exposure to normobaric hypoxia and this decline is not exacerbated by low intensity exercise.
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Affiliation(s)
- Chul-Ho Kim
- Exercise Physiology, School of Health Sciences, Kent State University, Kent, OH, USA; Human Integrative and Environmental Physiology, Mayo Clinic, Rochester, MN, USA.
| | - Edward J Ryan
- Exercise Physiology, School of Health Sciences, Kent State University, Kent, OH, USA; Department of Exercise Science, Chatham University, Pittsburgh, PA, USA
| | - Yongsuk Seo
- Exercise Physiology, School of Health Sciences, Kent State University, Kent, OH, USA
| | - Corey Peacock
- Exercise Physiology, School of Health Sciences, Kent State University, Kent, OH, USA
| | - John Gunstad
- Department of Psychology, Kent State University, Kent, OH, USA
| | - Matthew D Muller
- Exercise Physiology, School of Health Sciences, Kent State University, Kent, OH, USA; Penn State Heart & Vascular Institute, Penn State University College of Medicine, Hershey, PA, USA
| | - Angela L Ridgel
- Exercise Physiology, School of Health Sciences, Kent State University, Kent, OH, USA
| | - Ellen L Glickman
- Exercise Physiology, School of Health Sciences, Kent State University, Kent, OH, USA
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16
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Chapman RF, Laymon AS, Levine BD. Timing of arrival and pre-acclimatization strategies for the endurance athlete competing at moderate to high altitudes. High Alt Med Biol 2014; 14:319-24. [PMID: 24377334 DOI: 10.1089/ham.2013.1022] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
With the wide array of endurance sport competition offerings at moderate and high altitudes, clinicians are frequently asked about best practice recommendations regarding arrival times prior to the event and acclimatization guidelines. This brief review will offer data and current advice on when to arrive at altitude and various potential sea level-based pre-acclimatization strategies in an effort to maximize performance and minimize the risk of altitude sickness.
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Affiliation(s)
- Robert F Chapman
- 1 Human Performance Laboratory, Department of Kinesiology, Indiana University , Bloomington, Indiana
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17
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Beidleman BA, Fulco CS, Staab JE, Andrew SP, Muza SR. Cycling performance decrement is greater in hypobaric versus normobaric hypoxia. EXTREME PHYSIOLOGY & MEDICINE 2014; 3:8. [PMID: 24778792 PMCID: PMC4002198 DOI: 10.1186/2046-7648-3-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Accepted: 04/04/2014] [Indexed: 12/04/2022]
Abstract
BACKGROUND The purpose of this study was to determine whether cycling time trial (TT) performance differs between hypobaric hypoxia (HH) and normobaric hypoxia (NH) at the same ambient PO2 (93 mmHg, 4,300-m altitude equivalent). METHODS Two groups of healthy fit men were matched on physical performance and demographic characteristics and completed a 720-kJ time trial on a cycle ergometer at sea level (SL) and following approximately 2 h of resting exposure to either HH (n = 6, 20 ± 2 years, 75.2 ± 11.8 kg, mean ± SD) or NH (n = 6, 21 ± 3 years, 77.4 ± 8.8 kg). Volunteers were free to manually increase or decrease the work rate on the cycle ergometer. Heart rate (HR), arterial oxygen saturation (SaO2), and rating of perceived exertion (RPE) were collected every 5 min during the TT, and the mean was calculated. RESULTS Both groups exhibited similar TT performance (min) at SL (73.9 ± 7.6 vs. 73.2 ± 8.2), but TT performance was longer (P < 0.05) in HH (121.0 ± 12.1) compared to NH (99.5 ± 18.1). The percent decrement in TT performance from SL to HH (65.1 ± 23.6%) was greater (P < 0.05) than that from SL to NH (35.5 ± 13.7%). The mean exercise SaO2, HR, and RPE during the TT were not different in HH compared to NH. CONCLUSION Cycling time trial performance is impaired to a greater degree in HH versus NH at the same ambient PO2 equivalent to 4,300 m despite similar cardiorespiratory responses.
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Affiliation(s)
- Beth A Beidleman
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Kansas St., Bldg 42, Natick, MA 01760, USA
| | - Charles S Fulco
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Kansas St., Bldg 42, Natick, MA 01760, USA
| | - Janet E Staab
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Kansas St., Bldg 42, Natick, MA 01760, USA
| | - Sean P Andrew
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Kansas St., Bldg 42, Natick, MA 01760, USA
| | - Stephen R Muza
- Thermal and Mountain Medicine Division, United States Army Research Institute of Environmental Medicine, Kansas St., Bldg 42, Natick, MA 01760, USA
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Abstract
Acute mountain sickness (AMS) and large decrements in endurance exercise performance occur when unacclimatized individuals rapidly ascend to high altitudes. Six altitude and hypoxia preacclimatization strategies were evaluated to determine their effectiveness for minimizing AMS and improving performance during altitude exposures. Strategies using hypobaric chambers or true altitude were much more effective overall than those using normobaric hypoxia (breathing, <20.9% oxygen).
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Faulhaber M, Dünnwald T, Gatterer H, Bernardi L, Burtscher M. Metabolic adaptations may counteract ventilatory adaptations of intermittent hypoxic exposure during submaximal exercise at altitudes up to 4000 m. PLoS One 2012; 7:e49953. [PMID: 23166803 PMCID: PMC3498202 DOI: 10.1371/journal.pone.0049953] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Accepted: 10/18/2012] [Indexed: 01/17/2023] Open
Abstract
Intermittent hypoxic exposure (IHE) has been shown to induce aspects of altitude acclimatization which affect ventilatory, cardiovascular and metabolic responses during exercise in normoxia and hypoxia. However, knowledge on altitude-dependent effects and possible interactions remains scarce. Therefore, we determined the effects of IHE on cardiorespiratory and metabolic responses at different simulated altitudes in the same healthy subjects. Eight healthy male volunteers participated in the study and were tested before and 1 to 2 days after IHE (7×1 hour at 4500 m). The participants cycled at 2 submaximal workloads (corresponding to 40% and 60% of peak oxygen uptake at low altitude) at simulated altitudes of 2000 m, 3000 m, and 4000 m in a randomized order. Gas analysis was performed and arterial oxygen saturation, blood lactate concentrations, and blood gases were determined during exercise. Additionally baroreflex sensitivity, hypoxic and hypercapnic ventilatory response were determined before and after IHE. Hypoxic ventilatory response was increased after IHE (p<0.05). There were no altitude-dependent changes by IHE in any of the determined parameters. However, blood lactate concentrations and carbon dioxide output were reduced; minute ventilation and arterial oxygen saturation were unchanged, and ventilatory equivalent for carbon dioxide was increased after IHE irrespective of altitude. Changes in hypoxic ventilatory response were associated with changes in blood lactate (r = −0.72, p<0.05). Changes in blood lactate correlated with changes in carbon dioxide output (r = 0.61, p<0.01) and minute ventilation (r = 0.54, p<0.01). Based on the present results it seems that the reductions in blood lactate and carbon dioxide output have counteracted the increased hypoxic ventilatory response. As a result minute ventilation and arterial oxygen saturation did not increase during submaximal exercise at simulated altitudes between 2000 m and 4000 m.
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Affiliation(s)
- Martin Faulhaber
- Department of Sport Science, University Innsbruck, Innsbruck, Austria.
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20
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Debevec T, Mekjavic IB. Short intermittent hypoxic exposures augment ventilation but do not alter regional cerebral and muscle oxygenation during hypoxic exercise. Respir Physiol Neurobiol 2012; 181:132-42. [DOI: 10.1016/j.resp.2012.02.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Revised: 02/20/2012] [Accepted: 02/23/2012] [Indexed: 11/25/2022]
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21
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Rodway GW, Muza SR. Fighting in Thin Air: Operational Wilderness Medicine in High Asia. Wilderness Environ Med 2011; 22:297-303. [DOI: 10.1016/j.wem.2011.08.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Revised: 07/02/2011] [Accepted: 08/25/2011] [Indexed: 10/14/2022]
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Fulco CS, Muza SR, Beidleman BA, Demes R, Staab JE, Jones JE, Cymerman A. Effect of repeated normobaric hypoxia exposures during sleep on acute mountain sickness, exercise performance, and sleep during exposure to terrestrial altitude. Am J Physiol Regul Integr Comp Physiol 2011; 300:R428-36. [DOI: 10.1152/ajpregu.00633.2010] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
There is an expectation that repeated daily exposures to normobaric hypoxia (NH) will induce ventilatory acclimatization and lessen acute mountain sickness (AMS) and the exercise performance decrement during subsequent hypobaric hypoxia (HH) exposure. However, this notion has not been tested objectively. Healthy, unacclimatized sea-level (SL) residents slept for 7.5 h each night for 7 consecutive nights in hypoxia rooms under NH [ n = 14, 24 ± 5 (SD) yr] or “sham” ( n = 9, 25 ± 6 yr) conditions. The ambient percent O2 for the NH group was progressively reduced by 0.3% [150 m equivalent (equiv)] each night from 16.2% (2,200 m equiv) on night 1 to 14.4% (3,100 m equiv) on night 7, while that for the ventilatory- and exercise-matched sham group remained at 20.9%. Beginning at 25 h after sham or NH treatment, all subjects ascended and lived for 5 days at HH (4,300 m). End-tidal Pco2, O2 saturation (SaO2), AMS, and heart rate were measured repeatedly during daytime rest, sleep, or exercise (11.3-km treadmill time trial). From pre- to posttreatment at SL, resting end-tidal Pco2 decreased ( P < 0.01) for the NH (from 39 ± 3 to 35 ± 3 mmHg), but not for the sham (from 39 ± 2 to 38 ± 3 mmHg), group. Throughout HH, only sleep SaO2 was higher (80 ± 1 vs. 76 ± 1%, P < 0.05) and only AMS upon awakening was lower (0.34 ± 0.12 vs. 0.83 ± 0.14, P < 0.02) in the NH than the sham group; no other between-group rest, sleep, or exercise differences were observed at HH. These results indicate that the ventilatory acclimatization induced by NH sleep was primarily expressed during HH sleep. Under HH conditions, the higher sleep SaO2 may have contributed to a lessening of AMS upon awakening but had no impact on AMS or exercise performance for the remainder of each day.
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Affiliation(s)
- Charles S. Fulco
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Stephen R. Muza
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Beth A. Beidleman
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Robby Demes
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Janet E. Staab
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Juli E. Jones
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - Allen Cymerman
- Thermal and Mountain Medicine Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts
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Kenefick RW, Cheuvront SN, Palombo LJ, Ely BR, Sawka MN. Skin temperature modifies the impact of hypohydration on aerobic performance. J Appl Physiol (1985) 2010; 109:79-86. [DOI: 10.1152/japplphysiol.00135.2010] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study determined the effects of hypohydration on aerobic performance in compensable [evaporative cooling requirement (Ereq) < maximal evaporative cooling (Emax)] conditions of 10°C [7°C wet bulb globe temperature (WBGT)], 20°C (16°C WBGT), 30°C (22°C WBGT), and 40°C (27°C WBGT) ambient temperature (Ta). Our hypothesis was that 4% hypohydration would impair aerobic performance to a greater extent with increasing heat stress. Thirty-two men [22 ± 4 yr old, 45 ± 8 ml·kg−1·min−1 peak O2 uptake (V̇o2peak)] were divided into four matched cohorts ( n = 8) and tested at one of four Ta in euhydrated (EU) and hypohydrated (HYPO, −4% body mass) conditions. Subjects completed 30 min of preload exercise (cycle ergometer, 50% V̇o2peak) followed by a 15 min self-paced time trial. Time-trial performance (total work, change from EU) was −3% ( P = 0.1), −5% ( P = 0.06), −12% ( P < 0.05), and −23% ( P < 0.05) in 10°C, 20°C, 30°C, and 40°C Ta, respectively. During preload exercise, skin temperature (Tsk) increased by ∼4°C per 10°C Ta, while core (rectal) temperature (Tre) values were similar within EU and HYPO conditions across all Ta. A significant relationship ( P < 0.05, r = 0.61) was found between Tsk and the percent decrement in time-trial performance. During preload exercise, hypohydration generally blunted the increases in cardiac output and blood pressure while reducing blood volume over time in 30°C and 40°C Ta. Our conclusions are as follows: 1) hypohydration degrades aerobic performance to a greater extent with increasing heat stress; 2) when Tsk is >29°C, 4% hypohydration degrades aerobic performance by ∼1.6% for each additional 1°C Tsk; and 3) cardiovascular strain from high skin blood flow requirements combined with blood volume reductions induced by hypohydration is an important contributor to impaired performance.
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Affiliation(s)
- R. W. Kenefick
- US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - S. N. Cheuvront
- US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - L. J. Palombo
- US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - B. R. Ely
- US Army Research Institute of Environmental Medicine, Natick, Massachusetts
| | - M. N. Sawka
- US Army Research Institute of Environmental Medicine, Natick, Massachusetts
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Chapman RF, Stickford JL, Levine BD. Altitude training considerations for the winter sport athlete. Exp Physiol 2010; 95:411-21. [DOI: 10.1113/expphysiol.2009.050377] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Sightings edited by John W. Severinghaus. High Alt Med Biol 2009. [DOI: 10.1089/ham.2009.10403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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