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Prior heat stress: effect on subsequent 15-min time trial performance in the heat.
Med Sci Sports Exerc. 2009 Jun; 41(6):1311-6.MS

Abstract

The impact of prior heat stress on subsequent aerobic exercise-heat performance has not been studied.

PURPOSE

To determine whether prior heat stress degrades subsequent aerobic exercise performance in the heat.

METHODS

Eighteen nonheat acclimated males were trained (four practice trials) on an aerobic exercise performance test in 22 degrees C and then divided into two (n = 8) groups. One group (EUHPH; (.)VO2peak = 44 +/- 7 mL x kg x min(-1)) was tested after 90 min of recovery (in 22 degrees C) from 3 h of intermittent light-intensity (<30% (.)VO2peak) exercise-heat (50 degrees C) stress, where sweat losses were matched with fluid intake (3.5 +/- 0.5 L) to maintain euhydration. The other group (EUH; (.)VO2peak = 45 +/- 5 mL x kg x min(-1)) was tested while euhydrated without prior exercise-heat stress. Aerobic performance was determined from a 30-min cycling preload (50% (.)VO2peak) followed by a 15-min time trial in 40 degrees C. Total work during the 15-min performance time trial in EUH and EUHPH was compared, as were the percent changes from the best practice trials.

RESULTS

Volunteers were euhydrated (plasma osmolality < 290 mOsm x kg(-1)) and normothermic before each exercise-heat trial. Heart rate and core temperature were not different (P > 0.05) between groups at any time point during exercise. Total work was not different (P > 0.05) at baseline or between EUH (150.5 +/- 28.3 kJ; 2.0 +/- 0.3 kJ x kg(-1)) and EUHPH (160.3 +/- 24.0 kJ; 1.8 +/- 0.2 kJ x kg(-1)). The percent change in total work relative to baseline was not different (P > 0.05) between EUH (-18.7% +/- 9.2%) and EUHPH (-15.0% +/- 7.8%).

CONCLUSIONS

If hydration and body temperatures recover, prior exercise-heat stress does not result in a greater degradation in aerobic time trial performance in the heat compared with heat exposure alone.

Authors+Show Affiliations

US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA. Robert.Kenefick@us.army.milNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

19461533

Citation

Kenefick, Robert W., et al. "Prior Heat Stress: Effect On Subsequent 15-min Time Trial Performance in the Heat." Medicine and Science in Sports and Exercise, vol. 41, no. 6, 2009, pp. 1311-6.
Kenefick RW, Ely BR, Cheuvront SN, et al. Prior heat stress: effect on subsequent 15-min time trial performance in the heat. Med Sci Sports Exerc. 2009;41(6):1311-6.
Kenefick, R. W., Ely, B. R., Cheuvront, S. N., Palombo, L. J., Goodman, D. A., & Sawka, M. N. (2009). Prior heat stress: effect on subsequent 15-min time trial performance in the heat. Medicine and Science in Sports and Exercise, 41(6), 1311-6. https://doi.org/10.1249/MSS.0b013e3181988c14
Kenefick RW, et al. Prior Heat Stress: Effect On Subsequent 15-min Time Trial Performance in the Heat. Med Sci Sports Exerc. 2009;41(6):1311-6. PubMed PMID: 19461533.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Prior heat stress: effect on subsequent 15-min time trial performance in the heat. AU - Kenefick,Robert W, AU - Ely,Brett R, AU - Cheuvront,Samuel N, AU - Palombo,Laura J, AU - Goodman,Daniel A, AU - Sawka,Michael N, PY - 2009/5/23/entrez PY - 2009/5/23/pubmed PY - 2010/9/30/medline SP - 1311 EP - 6 JF - Medicine and science in sports and exercise JO - Med Sci Sports Exerc VL - 41 IS - 6 N2 - UNLABELLED: The impact of prior heat stress on subsequent aerobic exercise-heat performance has not been studied. PURPOSE: To determine whether prior heat stress degrades subsequent aerobic exercise performance in the heat. METHODS: Eighteen nonheat acclimated males were trained (four practice trials) on an aerobic exercise performance test in 22 degrees C and then divided into two (n = 8) groups. One group (EUHPH; (.)VO2peak = 44 +/- 7 mL x kg x min(-1)) was tested after 90 min of recovery (in 22 degrees C) from 3 h of intermittent light-intensity (<30% (.)VO2peak) exercise-heat (50 degrees C) stress, where sweat losses were matched with fluid intake (3.5 +/- 0.5 L) to maintain euhydration. The other group (EUH; (.)VO2peak = 45 +/- 5 mL x kg x min(-1)) was tested while euhydrated without prior exercise-heat stress. Aerobic performance was determined from a 30-min cycling preload (50% (.)VO2peak) followed by a 15-min time trial in 40 degrees C. Total work during the 15-min performance time trial in EUH and EUHPH was compared, as were the percent changes from the best practice trials. RESULTS: Volunteers were euhydrated (plasma osmolality < 290 mOsm x kg(-1)) and normothermic before each exercise-heat trial. Heart rate and core temperature were not different (P > 0.05) between groups at any time point during exercise. Total work was not different (P > 0.05) at baseline or between EUH (150.5 +/- 28.3 kJ; 2.0 +/- 0.3 kJ x kg(-1)) and EUHPH (160.3 +/- 24.0 kJ; 1.8 +/- 0.2 kJ x kg(-1)). The percent change in total work relative to baseline was not different (P > 0.05) between EUH (-18.7% +/- 9.2%) and EUHPH (-15.0% +/- 7.8%). CONCLUSIONS: If hydration and body temperatures recover, prior exercise-heat stress does not result in a greater degradation in aerobic time trial performance in the heat compared with heat exposure alone. SN - 1530-0315 UR - https://www.unboundmedicine.com/medline/citation/19461533/Prior_heat_stress:_effect_on_subsequent_15_min_time_trial_performance_in_the_heat_ DB - PRIME DP - Unbound Medicine ER -