Effects of active drinking practices on fluid consumption and sweat rate while exercising in a hot environment

J Exerc Nutrition Biochem. 2014 Jun;18(2):215-23. doi: 10.5717/jenb.2014.18.2.215. Epub 2014 Jun 10.

Abstract

Purpose: To examine the effects of active drinking practices on fluid consumption and sweat rate while exercising in a hot environment.

Methods: Nine men completed two experiments. Each consisted of 3 phases: pre-testing (pre), training period, and post-testing (post). During testing, the subjects ran on a treadmill at a moderate intensity for 90 min at 39 ± 1℃ followed by a 3-h recovery. They drank ad libitum. During training, they ran for 90 min for 7 days while either drinking actively (AH, 150% of weight loss) or passively (PH, 50% of weight loss).

Results: The actual volume consumed in training was three times greater during AH than during PH. In post during AH, the volume of drinking was two times greater than pre (1592 ± 953 and 855 ± 551 mL, respectively; p < 0.05). No difference in volume consumption during PH between pre and post was found. The sweat loss during exercise was greater in post (1377 ± 956 mL) than in pre (558 ± 642 mL) during AH (p < 0.05), but not during PH. Rectal temperature and heart rate decreased after training. Serum osmolality following exercise were not different than the baseline or between the conditions.

Conclusion: Active drinking practices while exercising in a hot environment induced greater voluntary fluid intake and sweat loss.

Keywords: rehydration; thermoregulation; voluntary intake.