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Effectiveness of short-term heat acclimation for highly trained athletes

Garrett, Andrew T.; Creasy, Rob; Rehrer, Nancy J.; Patterson, Mark J.; Cotter, James D.

Authors

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Dr Andrew Garrett A.Garrett@hull.ac.uk
Senior Lecturer in Exercise and Environmental Physiology

Rob Creasy

Nancy J. Rehrer

Mark J. Patterson

James D. Cotter



Abstract

Effectiveness of short-term acclimation has generally been undertaken using untrained and moderatelytrained participants. The purpose of this study was to determine the impact of short-term (5-day) heat acclimation on highly trained athletes. Eight males (mean ± SD age 21.8 ± 2.1 years, mass 75.2 ± 4.6 kg, _V O2peak 4.9 ± 0.2 L min-1 and power output 400 ± 27 W) were heat acclimated under controlled hyperthermia (rectal temperature 38.5C), for 90-min on five consecutive days (Ta = 39.5C, 60% relative humidity). Acclimation was undertaken with dehydration (no fluid-intake) during daily bouts. Participants completed a rowing-specific, heat stress test (HST) 1 day before and after acclimation (Ta = 35C, 60% relative humidity). HST consisted 10-min rowing at 30% peak power output (PPO), 10 min at 60% PPO and 5-min rest before a 2-km performance test, without feedback cues. Participants received 250 mL fluid (4% carbohydrate; osmolality 240-270 mmol kg-1) before the HST. Body mass loss during acclimation bouts was 1.6 ± 0.3 kg (2.1%) on day 1 and 2.3 ± 0.4 kg (3.0%) on day 5. In contrast, resting plasma volume increased by 4.5 ± 4.5% from day 1 to 5 (estimated from [Hb] & Hct). Plasma aldosterone increased at rest (52.6 pg mL-1; p = 0.03) and end-exercise (162.4 pg mL-1; p = 0.00) from day 1 to 5 acclimation. During the HST Tre and fc were lowered 0.3C (p = 0.00) and 14 b min-1 (p = 0.00) after 20-min exercise. The 2-km performance time (6.52.7 min) improved by 4 s (p = 0.00). Meaningful physiological and performance improvements occurred for highly trained athletes using a short-term (5-day) heat acclimation under hyperthermia control, with dehydration.

Journal Article Type Article
Publication Date 2012-05
Journal European Journal of Applied Physiology
Print ISSN 1439-6319
Electronic ISSN 1439-6327
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 112
Issue 5
Pages 1827-1837
APA6 Citation Garrett, A. T., Creasy, R., Rehrer, N. J., Patterson, M. J., & Cotter, J. D. (2012). Effectiveness of short-term heat acclimation for highly trained athletes. European journal of applied physiology, 112(5), (1827-1837). doi:10.1007/s00421-011-2153-3. ISSN 1439-6319
DOI https://doi.org/10.1007/s00421-011-2153-3
Keywords Elite; Performance; Dehydration; Fluid regulation; Plasma volume.
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