Temperate performance and metabolic adaptations following endurance training performed under environmental heat stress. Issue 9 (12th May 2021)

• Record Type: Journal Article
• Authors: Maunder, Ed; Plews, Daniel J.; Wallis, Gareth A.; Brick, Matthew J.; Leigh, Warren B.; Chang, Wee‐Leong; Watkins, Casey M.; Kilding, Andrew E.
• Is Part Of: Physiological reports. Volume 9:Issue 9(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-05-12
• Subjects: adaptation -- endurance training -- heat stress -- mitochondria -- performance; Physiology -- Periodicals; 571
• DOI: 10.14814/phy2.14849
• Languages: English
• ISSNs: 2051-817X

Abstract

Abstract: Endurance athletes are frequently exposed to environmental heat stress during training. We investigated whether exposure to 33°C during training would improve endurance performance in temperate conditions and stimulate mitochondrial adaptations. Seventeen endurance‐trained males were randomly assigned to perform a 3‐week training intervention in 18°C (TEMP) or 33°C (HEAT). An incremental test and 30‐min time‐trial preceded by 2‐h low‐intensity cycling were performed in 18°C pre‐ and post‐intervention, along with a resting vastus lateralis microbiopsy. Training was matched for relative cardiovascular demand using heart rates measured at the first and second ventilatory thresholds, along with a weekly "best‐effort" interval session. Perceived training load was similar between‐groups, despite lower power outputs during training in HEAT versus TEMP ( p < .05). Time‐trial performance improved to a greater extent in HEAT than TEMP (30 ± 13 vs. 16 ± 5 W, N = 7 vs. N = 6, p = .04), and citrate synthase activity increased in HEAT (fold‐change, 1.25 ± 0.25, p = .03, N = 9) but not TEMP (1.10 ± 0.22, p = .22, N = 7). Training‐induced changes in time‐trial performance and citrate synthase activity were related ( r = .51, p = .04). A group × time interaction for peak fat oxidation was observed (Δ 0.05 ± 0.14 vs. −0.09 ± 0.12 g·min −1 in TEMP and HEAT, N = 9 vs. N = 8, p = .05). Our data suggest exposure to moderate environmental heat stress during endurance training may be useful for inducing adaptations relevant to performance in temperate conditions. Abstract : We observed that 3 weeks of endurance training performed in 33°C improved endurance performance in temperate conditions to a significantly greater extent than matched training performed in 18°C. We also observed a significant increase in vastus lateralis citrate synthase activity in response to training performed in 33°C, but not matched training performed in 18°C.