Impairment of Cycling Capacity in the Heat in Well-Trained Endurance Athletes After High-Intensity Short-Term Heat Acclimation

Thomas Reeve, Ralph Gordon, Paul Laursen, Jason Lee, Christopher Tyler

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PURPOSE: To investigate the effects of short-term, high-intensity interval training (HIIT) on heat acclimation (HA).

METHODS: Male cyclists/triathletes were assigned into either an HA (n = 13) or a comparative (COMP, n = 10) group. HA completed 3 cycling heat-stress tests to exhaustion (60% Wmax) (HST1, pre-HA; HST2, post-HA; HST3, 7 d post-HA). HA consisted of 30-min bouts of HIIT cycling (6 min at 50% Wmax then 12 x 1 min 100%-Wmax bouts with 1 min rest between bouts) on 5 consecutive days. COMP completed HST1 and HST2 only. HST and HA trials were conducted in 35°C/50% relative humidity. Cycling capacity and physiological and perceptual data were recorded.

RESULTS:: Cycling capacity was impaired after HIIT HA (77.2 ± 34.2 min vs 56.2 ± 24.4 min, P = .03) and did not return to baseline after 7 d of no HA (59.2 ± 37.4 min). Capacity in HST1 and HST2 was similar in COMP (43.5 ± 8.3 vs 46.8 ± 15.7 min, P = .54). HIIT HA lowered resting rectal (37.0°C ± 0.3°C vs 36.8°C ± 0.2°C, P = .05) and body temperature (36.0°C ±0.3°C vs 35.8°C ± 0.3°C, P = .03) in HST2 compared with HST1 and lowered mean skin temperature (35.4°C ± 0.5°C vs 35.1°C ± 0.3°C, P = .02) and perceived strain on day 5 compared with day 1 of HA. All other data were unaffected.

CONCLUSIONS: Cycling capacity was impaired in the heat after 5 d of consecutive HIIT HA despite some heat adaptation. Based on the data, this approach is not recommended for athletes preparing to compete in the heat; however, it is possible that it may be beneficial if a state of overreaching is avoided.

© 2019, Human Kinetics. This is an author produced version of a paper published in INTERNATIONAL JOURNAL OF SPORTS PHYSIOLOGY AND PERFORMANCE uploaded in accordance with the publisher’s self- archiving policy. The final published version (version of record) is available online at the link below. Some minor differences between this version and the final published version may remain. We suggest you refer to the final published version should you wish to cite from it.
Original languageEnglish
Number of pages8
JournalInternational journal of sports physiology and performance
Early online date31 Jan 2019
Publication statusE-pub ahead of print - 31 Jan 2019

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