Bardis, C. N., Danias, K. S., Samara, E., Karagiorfoul, L., Stais, G., Axioti, E., Sidossis, L. S., & Kavouras, S. A. (2013). Prescribed hydration improves cycling performance in the heat. Medicine & Science in Sports & Exercise, 45(5), Supplement abstract number 311.

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This study investigated the effect of a prescribed protocol that matched fluid losses on repeated circuits of a hill-cycling performance during a course in the heat (~31.6C). Heat-acclimated, male endurance cyclists (N = 10) performed a cycling circuit on a laboratory ergometer. The circuit consisted of three sets of 5 km at 50% of maximum power output and 5 km of hill-grade (3%) race-pace cycling. Ss rode the performance test on two separate counterbalanced occasions while drinking water ad-libitum (as they wished) or following prescribed drinking (drinking every 1 km to match fluid losses). To design the prescribed drinking, Ss also performed a familiarization trial. Cyclists started the first 5 km climbing race-pace bout either in the prescribed-drinking trial at 0% loss or in the ad-libitum trial at ~-0.3% of body weight.

Time-to-completion for the third bout of the 5 km hill cycling was shorter in prescribed drinking than in the ad-libitum trial. Core, skin, and body temperatures immediately after the last hill climb were greater in the ad-libitum than in the prescribed-drinking trial. Overall, sweat sensitivity during the circuit course was lower in the ad-libitum trial than in the prescribed-drinking trial.

Implication. An individual hydration protocol improved cycling performance during repeated circuits of a hilly course in the heat when compared to ad-libitum drinking.

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