Effectiveness of short-term heat acclimation for highly trained athletes |
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Authors: | Email author" target="_blank">Andrew?T?GarrettEmail author Rob?Creasy Nancy?J?Rehrer Mark?J?Patterson James?D?Cotter |
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Institution: | (1) School of Physical Education, University of Otago, Dunedin, New Zealand;(2) Defence Science Technology Organisation (DSTO), Melbourne, Australia |
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Abstract: | Effectiveness of short-term acclimation has generally been undertaken using untrained and moderately-trained 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)\dot] \dot{V}O2peak 4.9 ± 0.2 L min−1 and power output 400 ± 27 W) were heat acclimated under controlled hyperthermia (rectal temperature 38.5°C), for 90-min on
five consecutive days (T
a = 39.5°C, 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 (T
a = 35°C, 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 T
re and f
c were lowered 0.3°C (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. |
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