Heat acclimatization does not improve (V) over dotO2max or cycling performance in a cool climate in trained cyclists

This study investigated if well-trained cyclists improve and performance in cool conditions following heat acclimatization through natural outdoor training in hot conditions. Eighteen trained male cyclists were tested for physiological adaptations, peak aerobic power output, exercise efficiency, and outdoor time trial (TT) performance (43.4km in cool environment, approximate to 5-13 degrees C) before and after 2 weeks of training in a cool (CON, n=9) or hot (approximate to 35 degrees C, HA, n=9) environment. After heat acclimatization, TT performance in the heat was improved by 16%; however, there was no change in the HA group in (4.79 +/- 0.21L/min vs 4.82 +/- 0.35L/min), peak aerobic power output (417 +/- 16W vs 422 +/- 17W), and outdoor TT performance in cool conditions (300 +/- 14W/69 +/- 3min vs 302 +/- 9W/69 +/- 4min). The present study shows that 2 weeks of heat acclimatization was associated with marked improvements in TT performance in the heat. However, for the well-trained endurance athletes, this did not transfer to an improved aerobic exercise capacity or outdoor TT performance in cool conditions.