Provision of instructions to drink ad libitum or according to thirst sensation: impact during 120 km of cycling in the heat in men

The terms drinking to thirst and ad libitum drinking are used interchangeably, but should they? We investigated the differences in how athletes consume fluids during exercise when instructed to drink according to thirst or ad libitum. Using a randomized, crossover and counterbalanced design, 10 males (27 4 y) cycled 120 km (48 4% of peak power, 33C, 40% relative humidity) on two occasions, while drinking water according to thirst or ad libitum. Participants covered the cycling trials in 222 11 min (p = 0.29). Although the body mass loss at the end of exercise and total volume of water consumed were similar between trials, thirst perception before each sip and the volume consumed per sip were significantly higher with thirst than ad libitum drinking, whereas the total number of sips was significantly lower with thirst than ad libitum drinking. Perceived exertion, rectal temperature and heart rate were all significantly higher with thirst than ad libitum drinking, but the difference was trivial. In conclusion, thirst and ad libitum drinking are associated with different drinking patterns, but equally maintain fluid balance during prolonged exercise. The terms drinking to thirst and ad libitum drinking can be used interchangeably for guiding fluid intake during prolonged exercise. NOVELTY • Both strategies are associated with different patterns of fluid ingestion during prolonged exercise, but are equally effective in maintaining fluid balance; • Perceived exertion, rectal temperature and heart rate are regulated dissimilarly by thirst and ad libitum drinking, but the difference is trivial.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author