Abstract

For standardisation purposes, studies adopting fixed, and often very large, fluid ingestion volumes were primarily used by expert bodies to develop their post-exercise fluid replacement guidelines. In addition, these studies mainly used exercise-induced dehydration methods. The aim of the present study was to assess whether voluntary post-exercise rehydration was influenced by the method of weight loss. Six recreationally active (4 male, 2 female) participants either remained euhydrated (EU) or reduced their body mass by 2% by 24h fluid restriction (FR), or a combination of intermittent exercise in the heat (34°C, 60% rh) followed by 13h fluid restriction (FREX). 15 min post-performance of a short maximal exercise capacity test, they remained in the laboratory for 60 min and voluntarily ingested a carbohydrate electrolyte drink (6% carbohydrate and 19 mM Na+) ad libitum. Drink volumes were monitored without participants knowledge at 10-, 30- and 60-min after the start of drinking and water intake from food and fluids was monitored for a further 240 min. Blood and urine samples were collected. Data were analysed using repeated measures ANOVA and are presented as mean (SD). Drink volumes ingested were unexpectedly high in all three conditions (Table 1), particularly on the EU trial where prior body mass losses were small(0.31 (0.11) kg). The nature of the exercise led to transient, but markedly elevated self-reported thirst and mouth dryness, serum sodium concentration and reduced plasma volume which may have driven these high drinking rates on the EU trial. Drink rates were greatest in the initial 10 min of fluid access, ranging between 40-50% of total fluid intake in the initial 60 min, but did not differ between trials. Total urine volume and net fluid balance were significantly greater in the EU trial compared with the FR and FREX trials, but did not differ between the FR and FREX trials. In conclusion, voluntary post-exercise fluid ingestion rates can be high and are similar despite varied methods of dehydration.