Prior heat sstress: Effect on subsequent 15-min time trial performance in the heat

Robert W. Kenefick, Brett R. Ely, Samuel N. Cheuvront, Laura J. Palombo, Daniel A. Goodman, Michael N. Sawka

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

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°C and then divided into two (n = 8) groups. One group (EUHPH; V̇O2peak = 44 ± 7 mL•kg•min) was tested after 90 min of recovery (in 22°C) from 3 h of intermittent light-intensity (<30% V̇O2peak) exercise-heat (50°C) stress, where sweat losses were matched with fluid intake (3.5 ± 0.5 L) to maintain euhydration. The other group (EUH; V̇O2peak = 45 ± 5 mL•kg•min) was tested while euhydrated without prior exercise-heat stress. Aerobic performance was determined from a 30-min cycling preload (50% V̇O2peak) followed by a 15-min time trial in 40°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•kg) 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•kg) and EUHPH (160.3 ± 24.0 kJ; 1.8 ± 0.2 kJ•kg). 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.

Original languageEnglish (US)
Pages (from-to)1311-1316
Number of pages6
JournalMedicine and science in sports and exercise
Volume41
Issue number6
DOIs
StatePublished - Jun 1 2009

Keywords

  • Dehydration
  • Fatigue
  • Heat strain
  • Methodology
  • Recovery
  • Subsequent exercise
  • Work in the heat

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

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