Effect of hypohydration and altitude exposure on aerobic exercise performance and acute mountain sickness

Hypoxia often causes body water deficits (hypohydration, HYPO); however, the effects of HYPO on aerobic exercise performance and prevalence of acute mountain sickness (AMS) at high altitude (ALT) have not been reported. We hypothesized that 1) HYPO and ALT would each degrade aerobic performance relative to sea level (SL)-euhydrated (EUH) conditions, and combining HYPO and ALT would further degrade performance more than one stressor alone; and 2) HYPO would increase the prevalence and severity of AMS symptoms. Seven lowlander men (25 ± 7 yr old; 82 ± 11 kg; mean ± SD) completed four separate experimental trials. Trials were 1) SL-EUH, 2) SL-HYPO, 3) ALT-EUH, and 4) ALT-HYPO. In HYPO, subjects were dehydrated by 4% of body mass. Subjects maintained hydration status overnight and the following morning entered a hypobaric chamber (at SL or 3,048 m, 27°C) where they completed 30 min of submaximal exercise immediately followed by a 30-min performance time trial (TT). AMS was measured with the Environmental Symptoms Questionnaire-Cerebral Score (AMS-C) and the Lake Louise Scoring System (LLS). The percent change in TT performance, relative to SL-EUH, was −19 ± 12% (334 ± 64 to 278 ± 87 kJ), −11 ± 10% (334 ± 64 to 293 ± 33 kJ), and −34 ± 22% (334 ± 64 to 227 ± 95 kJ), for SL-HYPO, ALT-EUH, and ALT-HYPO, respectively. AMS symptom prevalence was 2/7 subjects at ALT-EUH for AMS-C and LLS and 5/7 and 4/7 at ALT-HYPO for AMS-C and LLS, respectively. The AMS-C symptom severity score (AMS-C score) tended to increase from ALT-EUH to ALT-HYPO but was not significant ( P = 0.07). In conclusion, hypohydration at 3,048 m 1) degrades aerobic performance in an additive manner with that induced by ALT; and 2) did not appear to increase the prevalence/severity of AMS symptoms.

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Effect of repeated normobaric hypoxia exposures during sleep on acute mountain sickness, exercise performance, and sleep during exposure to terrestrial altitude

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00633.2010 ◽

2011 ◽

Vol 300 (2) ◽

pp. R428-R436 ◽

Cited By ~ 55

Author(s):

Charles S. Fulco ◽

Stephen R. Muza ◽

Beth A. Beidleman ◽

Robby Demes ◽

Janet E. Staab ◽

...

Keyword(s):

Heart Rate ◽

Exercise Performance ◽

Hypobaric Hypoxia ◽

Sham Group ◽

Acute Mountain Sickness ◽

Time Trial ◽

Normobaric Hypoxia ◽

Performance Decrement ◽

Mountain Sickness ◽

End Tidal

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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Effects of Ramadan Fasting on Body Composition, Aerobic Performance and Lactate, Heart Rate and Perceptual Responses in Young Soccer Players

Journal of Human Kinetics ◽

10.2478/v10078-011-0042-9 ◽

2011 ◽

Vol 29 (1) ◽

pp. 79-91 ◽

Cited By ~ 23

Author(s):

Alpay Güvenç

Keyword(s):

Heart Rate ◽

Body Composition ◽

Aerobic Exercise ◽

Blood Lactate ◽

Exercise Performance ◽

Perceived Exertion ◽

Soccer Players ◽

Aerobic Performance ◽

Hydration Status ◽

Ramadan Fasting

Effects of Ramadan Fasting on Body Composition, Aerobic Performance and Lactate, Heart Rate and Perceptual Responses in Young Soccer PlayersThe purpose of this study was to examine the effects of Ramadan fasting on body composition, aerobic exercise performance and blood lactate, heart rate and perceived exertion in regularly trained young soccer players. Sixteen male soccer players participated in this study. Mean age, stature, body mass and training age of the players were 17.4±1.2 years, 175.4±3.6 cm, 69.6±4.3 kg and 5.1±1.3 years, respectively. During the Ramadan period, all subjects voluntarily chose to follow the fasting guidelines and abstained from eating and drinking from sunrise to sunset. Body composition, hydration status, dietary intake and sleep duration were assessed on four occasions: before Ramadan, at the beginning of Ramadan, at the end of Ramadan and 2 weeks after the end of Ramadan. On each occasion, aerobic exercise performance and blood lactate, heart rate and rating of perceived exertion responses of players were also determined during an incremental running test. Repeated measures of ANOVA revealed that body mass, percentage of body fat, fat-free mass, hydration status, daily sleeping time and daily energy and macronutrient intake of players did not vary significantly throughout the study period (p>0.05). However, players experienced a small but significant decrease in skinfold thicknesses over the course of the study (p<0.05). Although ratings of perceived exertion at submaximal workloads increased during Ramadan (p<0.05), blood lactate and heart rate responses had decreased by the end of Ramadan (p<0.05). In line with these changes, peak running performance and running velocity at anaerobic threshold also improved by the end of Ramadan (p<0.05). Improvements in aerobic exercise performance with time were probably due to the effects of pre-season training program that was performed after the break of the fast (Iftar) during the month of Ramadan. The results of the present study suggest that if regular training regimen, body fluid balance, daily energy intake and sleep duration are maintained as before Ramadan, Ramadan fasting does not have detrimental effects on aerobic exercise performance or body composition in young soccer players.

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Acetazolamide does not alter endurance exercise performance at 3,500-m altitude

Journal of Applied Physiology ◽

10.1152/japplphysiol.00655.2019 ◽

2020 ◽

Vol 128 (2) ◽

pp. 390-396 ◽

Cited By ~ 6

Author(s):

Karleigh E. Bradbury ◽

Beau R. Yurkevicius ◽

Katherine M. Mitchell ◽

Kirsten E. Coffman ◽

Roy M. Salgado ◽

...

Keyword(s):

Sea Level ◽

Endurance Exercise ◽

Exercise Performance ◽

Repeated Measures ◽

Acute Mountain Sickness ◽

Time Trial ◽

Peak Oxygen Consumption ◽

Repeated Measures Design ◽

Hypoxic Environment ◽

The Impact

Acetazolamide (AZ) is a medication commonly used to prevent acute mountain sickness (AMS) during rapid ascent to high altitude. However, it is unclear whether AZ use impairs exercise performance; previous literature regarding this topic is equivocal. The purpose of this study was to evaluate the impact of AZ on time-trial (TT) performance during a 30-h exposure to hypobaric hypoxia equivalent to 3,500-m altitude. Ten men [sea-level peak oxygen consumption (VO2peak): 50.8 ± 6.5 mL·kg−1·min−1; body fat %: 20.6 ± 5.2%] completed 2 30-h exposures at 3,500 m. In a crossover study design, subjects were given 500 mg/day of either AZ or a placebo. Exercise testing was completed 2 h and 24 h after ascent and consisted of 15-min steady-state treadmill walking at 40%–45% sea-level VO2peak, followed by a 2-mile self-paced treadmill TT. AMS was assessed after ~12 h and 22 h at 3,500 m. The incidence of AMS decreased from 40% with placebo to 0% with AZ. Oxygen saturation was higher ( P < 0.05) in AZ versus placebo trials at the end of the TT after 2 h (85 ± 3% vs. 79 ± 3%) and 24 h (86 ± 3% vs. 81 ± 4%). There was no difference in time to complete 2 miles between AZ and PL after 2 h (20.7 ± 3.2 vs. 22.7 ± 5.0 min, P > 0.05) or 24 h (21.5 ± 3.4 vs. 21.1 ± 2.9 min, P > 0.05) of exposure to altitude. Our results suggest that AZ (500 mg/day) does not negatively impact endurance exercise performance at 3,500 m. NEW & NOTEWORTHY To our knowledge, this is the first study to examine the impact of acetazolamide (500 mg/day) versus placebo on self-paced, peak-effort exercise performance using a short-duration exercise test in a hypobaric hypoxic environment with a repeated-measures design. In the present study, acetazolamide did not impact exercise performance after 2-h or 24-h exposure to 3,500-m simulated altitude.

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The Influence of Heat Acclimation and Hypohydration on Post-Weight-Loss Exercise Performance

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2019-0092 ◽

2020 ◽

Vol 15 (2) ◽

pp. 213-221

Author(s):

Oliver R. Barley ◽

Dale W. Chapman ◽

Georgios Mavropalias ◽

Chris R. Abbiss

Keyword(s):

Body Mass ◽

Exercise Performance ◽

Fluid Intake ◽

Heat Acclimation ◽

Hydration Status ◽

Performance Variables ◽

Pooled Data ◽

Ad Libitum ◽

Experimental Trials ◽

Food And Fluid Intake

Purpose: To examine the influence of fluid intake on heat acclimation and the subsequent effects on exercise performance following acute hypohydration. Methods: Participants were randomly assigned to 1 of 2 groups, either able to consume water ad libitum (n = 10; age 23 [3] y, height 1.81 [0.09] m, body mass 87 [13] kg; HAW) or not allowed fluid (n = 10; age 26 [5] y, height 1.76 [0.05] m, body mass 79 [10] kg; HANW) throughout 12 × 1.5-h passive heat-acclimation sessions. Experimental trials were completed on 2 occasions before (2 baseline trials) and 1 following the heat-acclimation sessions. These sessions involved 3 h of passive heating (45°C, 38% relative humidity) to induce hypohydration followed by 3 h of ad libitum food and fluid intake after which participants performed a repeat sled-push test to assess physical performance. Urine and blood samples were collected before, immediately, and 3 h following hypohydration to assess hydration status. Mood was also assessed at the same time points. Results: No meaningful differences in physiological or performance variables were observed between HANW and HAW at any time point. Using pooled data, mean sprint speed was significantly (P < .001) faster following heat acclimation (4.6 [0.7] s compared with 5.1 [0.8] s). Furthermore, heat acclimation appeared to improve mood following hypohydration. Conclusions: Results suggest that passive heat-acclimation protocols may be effective at improving short-duration repeat-effort performance following acute hypohydration.

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Effect of 8 days of exercise-heat acclimation on aerobic exercise performance of men in hypobaric hypoxia

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00048.2020 ◽

2020 ◽

Vol 319 (1) ◽

pp. R114-R122

Author(s):

Roy M. Salgado ◽

Kirsten E. Coffman ◽

Karleigh E. Bradbury ◽

Katherine M. Mitchell ◽

Beau R. Yurkevicius ◽

...

Keyword(s):

Steady State ◽

Exercise Performance ◽

Hypobaric Hypoxia ◽

Acute Mountain Sickness ◽

Time Trial ◽

Heat Acclimation ◽

Peak Oxygen Consumption ◽

Time Trial Performance ◽

Expansion Time ◽

Trial Performance

Exercise-heat acclimation (EHA) induces adaptations that improve tolerance to heat exposure. Whether adaptations from EHA can also alter responses to hypobaric hypoxia (HH) conditions remains unclear. This study assessed whether EHA can alter time-trial performance and/or incidence of acute mountain sickness (AMS) during HH exposure. Thirteen sea-level (SL) resident men [SL peak oxygen consumption (V̇o2peak) 3.19 ± 0.43 L/min] completed steady-state exercise, followed by a 15-min cycle time trial and assessment of AMS before (HH1; 3,500 m) and after (HH2) an 8-day EHA protocol [120 min; 5 km/h; 2% incline; 40°C and 40% relative humidity (RH)]. EHA induced lower heart rate (HR) and core temperature and plasma volume expansion. Time-trial performance was not different between HH1 and HH2 after 2 h (106.3 ± 23.8 vs. 101.4 ± 23.0 kJ, P = 0.71) or 24 h (107.3 ± 23.4 vs. 106.3 ± 20.8 kJ, P > 0.9). From HH1 to HH2, HR and oxygen saturation, at the end of steady-state exercise and time-trial tests at 2 h and 24 h, were not different ( P > 0.05). Three of 13 volunteers developed AMS during HH1 but not during HH2, whereas a fourth volunteer only developed AMS during HH2. Heat shock protein 70 was not different from HH1 to HH2 at SL [1.9 ± 0.7 vs. 1.8 ± 0.6 normalized integrated intensities (NII), P = 0.97] or after 23 h (1.8 ± 0.4 vs. 1.7 ± 0.5 NII, P = 0.78) at HH. Our results indicate that this EHA protocol had little to no effect—neither beneficial nor detrimental—on exercise performance in HH. EHA may reduce AMS in those who initially developed AMS; however, studies at higher elevations, having higher incidence rates, are needed to confirm our findings.

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Voluntary fluid intake, hydration status, and aerobic performance of adolescent athletes in the heat

Applied Physiology Nutrition and Metabolism ◽

10.1139/h10-084 ◽

2010 ◽

Vol 35 (6) ◽

pp. 834-841 ◽

Cited By ~ 12

Author(s):

Boguslaw Wilk ◽

Brian W. Timmons ◽

Oded Bar-Or

Keyword(s):

Body Weight ◽

Oxygen Uptake ◽

Exercise Performance ◽

Fluid Intake ◽

Tap Water ◽

Peak Oxygen Uptake ◽

Adolescent Male ◽

Aerobic Performance ◽

Hydration Status ◽

Time To Exhaustion

We determined whether beverage flavoring and composition would stimulate voluntary drink intake, prevent dehydration, and maintain exercise performance in heat-acclimated adolescent males running in the heat. Eight adolescent (age, 13.7 ± 1.1 years) runners (peak oxygen uptake, 59.5 ± 4.0 mL·kg–1·min–1) underwent at least four 80-min exercise heat-acclimation sessions before completing 3 experimental sessions. All sessions were performed at 30 °C and 60%–65% relative humidity. Each experimental session consisted of five 15-min treadmill runs at a speed eliciting 65% peak oxygen uptake, with a 5 min rest prior to each run. Ten minutes after the final run, a time to exhaustion test was performed at a speed eliciting 90% peak oxygen uptake. Counterbalanced experimental sessions were identical, except for fluid intake, which consisted of tap water (W), flavored water (FW), and FW with 6% carbohydrate and 18 mmol·L–1 NaCl (CNa) consumed ad libitum. Fluid intake and body weight were monitored to calculate dehydration. Voluntary fluid intake was similar to fluid losses in W (1032 ± 130 vs. 1340 ± 246 g), FW (1086 ± 86 vs. 1451 ± 253 g), and CNa (1259 ± 119 vs. 1358 ± 234 g). As a result, significant dehydration was avoided in all trials (–0.45% ± 0.68% body weight in W, –0.66% ± 0.50% body weight in FW, and –0.13% ± 0.71% body weight in CNa). Core temperature increased by ~1 °C during exercise, but was not different between trials. Time to exhaustion was not different between trials and averaged 8.8 ± 1.7 min. Under exercise conditions more closely reflecting real-life situations, heat-acclimatized adolescent male runners can appropriately gauge fluid intake regardless of the type of beverage made available, resulting in consistency in exercise performance.

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Postexercise Glycogen Recovery and Exercise Performance is Not Significantly Different Between Fast Food and Sport Supplements

International Journal of Sport Nutrition and Exercise Metabolism ◽

10.1123/ijsnem.2014-0230 ◽

2015 ◽

Vol 25 (5) ◽

pp. 448-455 ◽

Cited By ~ 5

Author(s):

Michael J. Cramer ◽

Charles L. Dumke ◽

Walter S. Hailes ◽

John S. Cuddy ◽

Brent C. Ruby

Keyword(s):

Exercise Performance ◽

Fast Food ◽

Vastus Lateralis ◽

Recovery Period ◽

Time Trial ◽

Past Research ◽

Glycogen Depletion ◽

Post Exercise ◽

Sport Supplements ◽

Experimental Trials

A variety of dietary choices are marketed to enhance glycogen recovery after physical activity. Past research informs recommendations regarding the timing, dose, and nutrient compositions to facilitate glycogen recovery. This study examined the effects of isoenergetic sport supplements (SS) vs. fast food (FF) on glycogen recovery and exercise performance. Eleven males completed two experimental trials in a randomized, counterbalanced order. Each trial included a 90-min glycogen depletion ride followed by a 4-hr recovery period. Absolute amounts of macronutrients (1.54 ± 0.27 g·kg-1 carbohydrate, 0.24 ± 0.04 g·kg fat-1, and 0.18 ± 0.03g·kg protein-1) as either SS or FF were provided at 0 and 2 hr. Muscle biopsies were collected from the vastus lateralis at 0 and 4 hr post exercise. Blood samples were analyzed at 0, 30, 60, 120, 150, 180, and 240 min post exercise for insulin and glucose, with blood lipids analyzed at 0 and 240 min. A 20k time-trial (TT) was completed following the final muscle biopsy. There were no differences in the blood glucose and insulin responses. Similarly, rates of glycogen recovery were not different across the diets (6.9 ± 1.7 and 7.9 ± 2.4 mmol·kg wet weight- 1·hr-1 for SS and FF, respectively). There was also no difference across the diets for TT performance (34.1 ± 1.8 and 34.3 ± 1.7 min for SS and FF, respectively. These data indicate that short-term food options to initiate glycogen resynthesis can include dietary options not typically marketed as sports nutrition products such as fast food menu items.

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Exercise under heat stress: thermoregulation, hydration, performance implications and mitigation strategies

Physiological Reviews ◽

10.1152/physrev.00038.2020 ◽

2021 ◽

Author(s):

Julien D. Periard ◽

Thijs M.H. Eijsvogels ◽

Hein A.M. Daanen

Keyword(s):

Heat Stress ◽

Exercise Performance ◽

Thermal Strain ◽

Mitigation Strategies ◽

Body Core Temperature ◽

Aerobic Performance ◽

Future Research ◽

Hydration Status ◽

Fatigue Development ◽

The Impact

A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and integrative overview of how the human body responds to exercise under heat stress and the countermeasures that can be adopted to enhance aerobic performance under such environmental conditions. The fundamental concepts and physiological processes associated with thermoregulation and fluid balance are initially described, followed by a summary of methods to determine thermal strain and hydration status. An outline is provided on how exercise-heat stress disrupts these homeostatic processes, leading to hyperthermia, hypohydration, sodium disturbances and in some cases exertional heat illness. The impact of heat stress on human performance is also examined, including the underlying physiological mechanisms that mediate the impairment of exercise performance. Similarly, the influence of hydration status on performance in the heat and how systemic and peripheral hemodynamic adjustments contribute to fatigue development is elucidated. This review also discusses strategies to mitigate the effects of hyperthermia and hypohydration on exercise performance in the heat, by examining the benefits of heat acclimation, cooling strategies and hyperhydration. Finally, contemporary controversies are summarized and future research directions provided.

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Acute Sodium Ingestion Before Exercise Increases Voluntary Water Consumption Resulting in Preexercise Hyperhydration and Improvement in Exercise Performance in the Heat

International Journal of Sport Nutrition and Exercise Metabolism ◽

10.1123/ijsnem.2014-0212 ◽

2015 ◽

Vol 25 (5) ◽

pp. 456-462 ◽

Cited By ~ 5

Author(s):

David M. Morris ◽

Joshua R. Huot ◽

Adam M. Jetton ◽

Scott R. Collier ◽

Alan C. Utter

Keyword(s):

Water Consumption ◽

Exercise Performance ◽

Time Trial ◽

Favorable Effect ◽

Hydration Status ◽

Performance Time ◽

Sodium Ingestion ◽

Improve Exercise Performance ◽

And Performance ◽

Sodium Consumption

Dehydration has been shown to hinder performance of sustained exercise in the heat. Consuming fluids before exercise can result in hyperhydration, delay the onset of dehydration during exercise and improve exercise performance. However, humans normally drink only in response to thirst, which does not result in hyperhydration. Thirst and voluntary fluid consumption have been shown to increase following oral ingestion or infusion of sodium into the bloodstream. We measured the effects of acute sodium ingestion on voluntary water consumption and retention during a 2-hr hydration period before exercise. Subjects then performed a 60-min submaximal dehydration ride (DR) followed immediately by a 200 kJ performance time trial (PTT) in a warm (30 °C) environment. Water consumption and retention during the hydration period was greater following sodium ingestion (1380 ± 580 mL consumed, 821 ± 367 ml retained) compared with placebo (815 ± 483 ml consumed, 244 ± 402 mL retained) and no treatment (782 ± 454 ml consumed, 148 ± 289 mL retained). Dehydration levels following the DR were significantly less after sodium ingestion (0.7 ± 0.6%) compared with placebo (1.3 ± 0.7%) and no treatment (1.6 ± 0.4%). Time to complete the PTT was significantly less following sodium consumption (773 ± 158 s) compared with placebo (851 ± 156 s) and no treatment (872 ± 190 s). These results suggest that voluntary hyperhydration can be induced by acute consumption of sodium and has a favorable effect on hydration status and performance during subsequent exercise in the heat.

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