Author(s): RAMOS, J., DUCKER, K., RIDDELL, H., LANDERS, G., GIRARD, O., BRADE, C., Institution: CURTIN UNIVERSITY, Country: AUSTRALIA, Abstract-ID: 144

INTRODUCTION:
Heat acclimation (HA) is critical to mitigate the adverse effects of heat on exercise performance. While these methods yield physiological adaptations to heat, it also results in greater internal training load. This can potentially compromise training quality and lead to overreaching. Therefore, there is a need for HA protocols that address situations where training quality is crucial, yet the heat stimulus is necessary. The aim of this study was to investigate the influence of shorter, more frequent rest breaks with per-cooling as an alternative heat acclimation session on physiological, perceptual, and self-paced maximal cycling performance, compared to continuous heat exposure.
METHODS:
Thirteen participants completed one continuous and three intermittent heat exposure (IHE) maximal self-paced cycling protocols in a random order in heat (36°C, 80% relative humidity): 1 x 60-min exercise (CON), 3 x 20-min exercise with 7.5-min rest between sets (IHE-20), 4 x 15-min exercise with 5-min rest between sets (IHE-15), 6 x 10-min exercise with 3-min rest between sets (IHE-10). Mixed-method PerC (crushed-ice ingestion and cooling vest) was applied during rest periods of all IHE protocols.
RESULTS:
Total distance completed was greater in IHE-10, IHE-15, and IHE-20 compared to CON (+11%, +9%, and +8%, respectively), with no difference observed between IHE protocols. Total time spent above 38.5°C core temperature was longer in CON compared to IHE-15 and IHE-20 (+62% and +78%, respectively), but similar to IHE-10 (+5%). Furthermore, a longer time above 38.5°C core temperature occurred in IHE-10 versus IHE-15 and IHE-20 (+54% and +69%, respectively). Greater mean skin temperature over time was observed in CON than all IHE protocols (IHE-10: β=.02, t[584]=4.68, p<.01, IHE-15: β=.02, t[584]=5.07, p<.01, IHE-20: β=.02, t[584]=4.69, p<.01). No significant difference between IHE protocols was observed. Sweat loss did not differ between conditions.
CONCLUSION:
Intermittent heat exposure with per-cooling resulted in increased training intensity compared to traditional continuous heat exposure. Despite the shorter exercise duration and more frequent breaks in IHE-10, the necessary stimulus (e.g., time above 38.5°C core temperature) and physiological responses (e.g., sweat loss) required for effective HA were not compromised. This can be attributed to lower core and skin temperature as well as improved perceptual responses when PerC was applied.