Changes in the physiological strain and graded exercise performance due to warming or cooling of the lower body in a temperate environment

Context: Anecdotal reports suggest elite sports clubs combine lower-body positive-pressure rehabilitation with a hypoxic stimulus to maintain or increase physiological and metabolic strain, which are reduced during lower-body positive pressure. However, the effects of hypoxia on cardiovascular and metabolic response during lower-body positive-pressure rehabilitation are unknown. Objective: Evaluate the use of normobaric hypoxia as a means to increase physiological strain during body-weight-supported (BWS) running. Design: Crossover study. Setting: Controlled laboratory. Participants: Seven familiarized males (mean (SD): age, 20 (1) y; height, 1.77 (0.05) m; mass, 69.4 (5.1) kg; hemoglobin, 15.2 (0.8) g·dL−1) completed a normoxic and hypoxic (fraction of inspired oxygen [O2] = 0.14) trial, during which they ran at 8 km·h−1 on an AlterG™ treadmill with 0%, 30%, and 60% BWS in a randomized order for 10 minutes interspersed with 5 minutes of recovery. Main Outcome Measures: Arterial O2 saturation, heart rate, O2 delivery, and measurements of metabolic strain via indirect calorimetry. Results: Hypoxic exercise reduced hemoglobin O2 saturation and elevated heart rate at each level of BWS compared with normoxia. However, the reduction in hemoglobin O2 saturation was attenuated at 60% BWS compared with 0% and 30%, and consequently, O2 delivery was better maintained at 60% BWS. Conclusion: Hypoxia is a practically useful means of increasing physiological strain during BWS rehabilitation. In light of the maintenance of hemoglobin O2 saturation and O2 delivery at increasing levels of BWS, fixed hemoglobin saturations rather than a fixed altitude are recommended to maintain an aerobic stimulus.

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The Influence of Hot Humid and Hot Dry Environments on Intermittent-Sprint Exercise Performance

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2012-0247 ◽

2014 ◽

Vol 9 (3) ◽

pp. 387-396 ◽

Cited By ~ 15

Author(s):

Mark Hayes ◽

Paul C. Castle ◽

Emma Z. Ross ◽

Neil S. Maxwell

Keyword(s):

Heat Stress ◽

Exercise Performance ◽

Peak Power ◽

Team Sport ◽

Peak Power Output ◽

Evaporative Heat Loss ◽

Physiological Strain ◽

Type Method ◽

Sprint Exercise ◽

Full Protocol

Purpose:To examine the effect of a hot humid (HH) compared with a hot dry (HD) environment, matched for heat stress, on intermittent-sprint performance. In comparison with HD, HH environments compromise evaporative heat loss and decrease exercise tolerance. It was hypothesized that HH would produce greater physiological strain and reduce intermittent-sprint exercise performance compared with HD.Method:Eleven male team-sport players completed the cycling intermittent-sprint protocol (CISP) in 3 conditions, temperate (TEMP; 21.2°C ± 1.3°C, 48.6% ± 8.4% relative humidity [rh]), HH (33.7°C ± 0.5°C, 78.2% ± 2.3% rh), and HD (40.2°C ± 0.2°C, 33.1% ± 4.9% rh), with both heat conditions matched for heat stress.Results:All participants completed the CISP in TEMP, but 3 failed to completed the full protocol of 20 sprints in HH and HD. Peak power output declined in all conditions (P < .05) but was not different between any condition (sprints 1–14 [N = 11]: HH 1073 ± 150 W, HD 1104 ± 127 W, TEMP, 1074 ± 134; sprints 15–20 [N = 8]: HH 954 ± 114 W, HD 997 ± 115 W, TEMP 993 ± 94; P > .05). Physiological strain was not significantly different in HH compared with HD, but HH was higher than TEMP (P < .05).Conclusion:Intermittent-sprint exercise performance of 40 min duration is impaired, but it is not different in HH and HD environments matched for heat stress despite evidence of a trend toward greater physiological strain in an HH environment.

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The Effects of 3 Different Doses of Caffeine on Jumping and Throwing Performance: A Randomized, Double-Blind, Crossover Study

International Journal of Sports Physiology and Performance ◽

10.1123/ijspp.2018-0884 ◽

2019 ◽

Vol 14 (9) ◽

pp. 1170-1177 ◽

Cited By ~ 18

Author(s):

Filip Sabol ◽

Jozo Grgic ◽

Pavle Mikulic

Keyword(s):

Exercise Performance ◽

Repeated Measures ◽

Vertical Jump ◽

Caffeine Intake ◽

Lower Body ◽

Acute Effects ◽

Experimental Conditions ◽

Caffeine Ingestion ◽

Ballistic Exercise ◽

Medicine Ball

Purpose: To examine the acute effects of 3 doses of caffeine on upper- and lower-body ballistic exercise performance and to explore if habitual caffeine intake affects the acute effects of caffeine ingestion on ballistic exercise performance. Methods: Twenty recreationally active male participants completed medicine-ball-throw and vertical-jump tests under 4 experimental conditions (placebo and 2, 4, and 6 mg·kg−1 of caffeine). Results: One-way repeated-measures analysis of variance (ANOVA) with subsequent post hoc analyses indicated that performance in the medicine-ball-throw test improved, compared with placebo, only with a 6 mg·kg−1 dose of caffeine (P = .032). Effect size, calculated as the mean difference between the 2 measurements divided by the pooled SD, amounted to 0.29 (+3.7%). For the vertical-jump test, all 3 caffeine doses were effective (compared with placebo) for acute increases in performance (P values .022–.044, effect sizes 0.35–0.42, percentage changes +3.7% to +4.1%). A 2-way repeated-measures ANOVA indicated that there was no significant group × condition interaction effect, suggesting comparable responses between low (≤100 mg·d−1) and moderate to high (>100 mg·d−1) caffeine users to the experimental conditions. Conclusion: Caffeine doses of 2, 4, and 6 mg·kg−1 seem to be effective for acute enhancements in lower-body ballistic exercise performance in recreationally trained male individuals. For the upper-body ballistic exercise performance, only a caffeine dose of 6 mg·kg−1 seems to be effective. The acute effects of caffeine ingestion do not seem to be affected by habitual caffeine intake; however, this requires further exploration.

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Separate and combined influences of heat and hypobaric hypoxia on self-paced aerobic exercise performance

Journal of Applied Physiology ◽

10.1152/japplphysiol.00023.2019 ◽

2019 ◽

Vol 127 (2) ◽

pp. 513-519 ◽

Cited By ~ 9

Author(s):

Karleigh E. Bradbury ◽

Kirsten E. Coffman ◽

Katherine M. Mitchell ◽

Adam J. Luippold ◽

Charles S. Fulco ◽

...

Keyword(s):

Exercise Performance ◽

Hypobaric Hypoxia ◽

Perceived Exertion ◽

Time Trial ◽

Work Rate ◽

Total Work ◽

Physiological Strain ◽

Cycling Time Trial ◽

C 30 ◽

Cycling Time

Heat and hypobaric hypoxia independently compromise exercise performance; however, their combined impact on exercise performance has yet to be quantified. This study examined the effects of heat, hypobaric hypoxia, and the combination of these environments on self-paced cycling time trial (TT) performance. Twelve subjects [2 female, 10 male; sea level (SL) peak oxygen consumption (V̇o2peak), 41.5 ± 4.4 mL·kg−1·min−1, mean ± SD] completed 30 min of steady-state cycling exercise (50% SL V̇o2peak), followed by a 15-min self-paced TT in four environmental conditions: SL thermoneutral [SLTN; 250 m, 20°C, 30–50% relative humidity (rh)], SL hot (SLH; 250 m, 35°C, 30% rh), hypobaric hypoxia thermoneutral (HTN; 3,000 m, 20°C, 30–50% rh), and hypobaric hypoxia hot (HH; 3,000 m, 35°C, 30% rh). Performance was assessed by the total work (kJ) completed. TT performance was lower ( P < 0.05) in SLH, HTN, and HH relative to SLTN (−15.4 ± 9.7, −24.1 ± 16.2, and −33.1 ± 13.4 kJ, respectively). Additionally, the total work completed in HTN and HH was lower ( P < 0.05) than that in SLH. In SLH, HTN, and HH, work rate was reduced versus SLTN ( P < 0.05) within the first 3 min of exercise and was consistent for the remainder of the bout. No differences ( P > 0.05) existed for heart rate or Ratings of Perceived Exertion at the end of exercise among conditions. The decrease in self-paced TT performance in the heat and/or hypobaric hypoxia conditions compared with SLTN conditions resulted from a nearly immediate reduction in work rate that may have been regulated by environmentally induced changes in physiological strain and perception of effort in response to TT exercise. NEW & NOTEWORTHY This is the first known study to examine the combined effects of heat and hypobaric hypoxia on short-duration self-paced cycling time trial performance. Regardless of environmental condition, subjects utilized an even work rate for the entire duration of the time trial. The presence of both environmental stressors led to a greater performance impairment than heat or hypobaric hypoxia alone, and the performance decrement stemmed from an early reduction of work rate.

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Influence of the Lower Body on Seated Arm Cranking Performance

International Journal of Sports Medicine ◽

10.1055/a-0633-9188 ◽

2018 ◽

Vol 39 (10) ◽

pp. 757-763 ◽

Cited By ~ 1

Author(s):

Ashley VanSumeren ◽

Thomas Bye ◽

Matthew Kilgas ◽

Matthew Hartvigsen ◽

Steven Elmer

Keyword(s):

Short Duration ◽

Peak Oxygen Consumption ◽

Upper Body ◽

Lower Body ◽

Maximal Power ◽

Physiological Strain ◽

Arm Cranking ◽

Integral Role ◽

Generating Capacity ◽

Incremental Protocol

AbstractDuring upper-body tasks, use of the lower body is important for minimizing physiological strain and maximizing performance. The lower body has an integral role during standing upper-body tasks, however, it is less clear if it is also important during seated upper-body tasks. We determined the extent to which the lower body influenced seated arm cranking performance. Eleven males performed incremental (40+20 W·3 min−1) and short-duration maximal effort (5 s, 120 rpm) arm cranking trials with and without lower-body restriction. The lower body was restricted by securing the legs to the seat and suspending them off the floor. Upper-body peak oxygen consumption (V̇O2peak) and maximal power were determined. At the end of the incremental protocol, lower-body restriction reduced V̇O2peak by 14±12% (P<0.01) compared to normal arm cranking. At greater submaximal stages (60-100% isotime) heart rate, ventilation, RER, and arm-specific exertion increased to a greater extent (all P<0.05) with lower-body restriction. During short duration maximal arm cranking, lower-body restriction decreased maximal power by 23±9% (P<0.01). Results indicated that lower-body restriction limited aerobic capacity, increased physiological strain during high-intensity submaximal exercise, and compromised maximal power generating capacity. These results imply that use of the lower body is critical when performing seated arm cranking. Our findings have implications for exercise testing, training and rehabilitation.

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Rehydration with fluid of varying tonicities: effects on fluid regulatory hormones and exercise performance in the heat

Journal of Applied Physiology ◽

10.1152/japplphysiol.00920.2006 ◽

2007 ◽

Vol 102 (5) ◽

pp. 1899-1905 ◽

Cited By ~ 28

Author(s):

R. W. Kenefick ◽

C. M. Maresh ◽

L. E. Armstrong ◽

D. Riebe ◽

M. E. Echegaray ◽

...

Keyword(s):

Body Weight ◽

Plasma Volume ◽

Exercise Performance ◽

Maximal Oxygen Consumption ◽

Urine Volume ◽

Plasma Osmolality ◽

Rest Period ◽

Physiological Strain ◽

Routes Of Administration ◽

Percent Change

This study examined the effects of rehydration (Rehy) with fluids of varying tonicities and routes of administration after exercise-induced hypohydration on exercise performance, fluid regulatory hormone responses, and cardiovascular and thermoregulatory strain during subsequent exercise in the heat. On four occasions, eight men performed an exercise-dehydration protocol of ∼185 min (33°C) to establish a 4% reduction in body weight. Following dehydration, 2% of the fluid lost was replaced during the first 45 min of a 100-min rest period by one of three random Rehy treatments (0.9% saline intravenous; 0.45% saline intravenous; 0.45% saline oral) or no Rehy (no fluid) treatment. Subjects then stood for 20 min at 36°C and then walked at 50% maximal oxygen consumption for 90 min. Subsequent to dehydration, plasma Na+, osmolality, aldosterone, and arginine vasopressin concentrations were elevated ( P < 0.05) in each trial, accompanied by a −4% hemoconcentration. Following Rehy, there were no differences ( P > 0.05) in fluid volume restored, post-rehydration (Post-Rehy) body weight, or urine volume. Percent change in plasma volume was 5% above pre-Rehy values, and plasma Na+, osmolality, and fluid regulatory hormones were lower compared with no fluid. During exercise, skin and core temperatures, heart rate, and exercise time were not different ( P > 0.05) among the Rehy treatments. Plasma osmolality, Na+, percent change in plasma volume, and fluid regulatory hormones responded similarly among all Rehy treatments. Neither a fluid of greater tonicity nor the route of administration resulted in a more rapid or greater fluid retention, nor did it enhance heat tolerance or diminish physiological strain during subsequent exercise in the heat.

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