Samuel T Tebeck1,2, Jonathan D Buckley2, Clint R Bellenger1,2,3, Jamie Stanley1,2,4. 1. 1 Department of Sports Science, South Australian Sports Institute, Adelaide, SA, Australia. 2. 2 Alliance for Research in Exercise, Nutrition and Activity (ARENA), Sansom Institute for Health Research, University of South Australia, Adelaide, SA, Australia. 3. 3 Department of Physiology, Australian Institute of Sport, Bruce, ACT, Australia. 4. 4 Australian Cycling Team, Cycling Australia, Kidman Park, SA, Australia.
Abstract
PURPOSE: To investigate the effect of a 5-day short-term heat acclimation (STHA) protocol in dry (43˚C and 20 % RH) or humid (32˚C and 80 % RH) environmental conditions on endurance cycling performance in temperate conditions (21˚C). METHODS: In a randomised, cross-over design, eleven cyclists completed each of the two, 5-day blocks of STHA matched for heat index (44˚C) and total exposure time (480 min), separated by 30-days. Pre- and post-temperate endurance performance (4-min mean max power, lactate threshold 1 and 2) was assessed in addition a heat stress test used to assess individual levels of heat adaptation. RESULTS: Differences in endurance performance were unclear. Following dry STHA, gross mechanical efficiency was likely reduced [between-condition effect size dry vs humid (90 % confidence interval) [-0.59 (-1.05, -0.15)], oxygen uptake was likely increased for a given workload [+0.64 (0.14, 1.07)] and energy expenditure likely increased [+0.59 (0.17, 1.03)]. Plasma volume expansion at Day 5 of acclimation was similar (within-condition outcome +4.6 ± 6.3 % and +5.3 ± 5.1 % dry and humid respectively) but was retained for 3-4 days longer after the final humid STHA exposure (-0.2 ± 8.1 % and +4.5 ± 4.2 % dry and humid respectively). Sweat rate was very likely increased during dry STHA [+0.57 (0.25, 0.89)] and possibly increased [+0.18 (-0.15; 0.50)] during humid STHA. CONCLUSION: STHA induced divergent adaptations between dry and humid conditions, but did not result in differences in temperate endurance performance.
PURPOSE: To investigate the effect of a 5-day short-term heat acclimation (STHA) protocol in dry (43˚C and 20 % RH) or humid (32˚C and 80 % RH) environmental conditions on endurance cycling performance in temperate conditions (21˚C). METHODS: In a randomised, cross-over design, eleven cyclists completed each of the two, 5-day blocks of STHA matched for heat index (44˚C) and total exposure time (480 min), separated by 30-days. Pre- and post-temperate endurance performance (4-min mean max power, lactate threshold 1 and 2) was assessed in addition a heat stress test used to assess individual levels of heat adaptation. RESULTS: Differences in endurance performance were unclear. Following dry STHA, gross mechanical efficiency was likely reduced [between-condition effect size dry vs humid (90 % confidence interval) [-0.59 (-1.05, -0.15)], oxygen uptake was likely increased for a given workload [+0.64 (0.14, 1.07)] and energy expenditure likely increased [+0.59 (0.17, 1.03)]. Plasma volume expansion at Day 5 of acclimation was similar (within-condition outcome +4.6 ± 6.3 % and +5.3 ± 5.1 % dry and humid respectively) but was retained for 3-4 days longer after the final humid STHA exposure (-0.2 ± 8.1 % and +4.5 ± 4.2 % dry and humid respectively). Sweat rate was very likely increased during dry STHA [+0.57 (0.25, 0.89)] and possibly increased [+0.18 (-0.15; 0.50)] during humid STHA. CONCLUSION: STHA induced divergent adaptations between dry and humid conditions, but did not result in differences in temperate endurance performance.
Authors: Yasuki Sekiguchi; Courteney L Benjamin; Elaine C Lee; Jeb F Struder; Ciara N Manning; Margaret C Morrissey; Michael R Szymanski; Rebecca L Stearns; Lawrence E Armstrong; Douglas J Casa Journal: Int J Environ Res Public Health Date: 2022-05-25 Impact factor: 4.614
Authors: Oliver R Gibson; Carl A James; Jessica A Mee; Ashley G B Willmott; Gareth Turner; Mark Hayes; Neil S Maxwell Journal: Temperature (Austin) Date: 2019-10-12