Fluid-regulating hormones’ responses after the ingestion of carbohydrate-electrolyte-whey protein solution during post-exercise recovery

Dehydration is commonly observed after exercise, which may impair the exercise performance and cognitive functions. Compared with carbohydrate-electrolyte (CE) solution, the co-ingestion of CE solution and whey protein is found to improve the post-exercise rehydration; however, the potential mechanisms underlying the findings are not clear. PURPOSE: To investigate the responses of fluid-regulating hormones after the ingestion of CE solution with or without whey protein during post-exercise recovery. METHODS: Ten males (age: 22.0 ± 0.7 years; VO2max: 59.8 ± 1.9 ml/kg/min) completed 3 trials in a randomized crossover design. A 4-hour recovery was applied in each trial after 60 min run at 65% VO2max, during which the subjects ingested either a CE-H solution (66 g/L carbohydrate), a CE-L solution (33 g/L carbohydrate), or a CW solution (33 g/L carbohydrate, 33 g/L whey protein). All solutions were matched for their electrolytes content (Na+: 21 mmol/L; K+: 3.3 mmol/L). The total solution volume was equal to 150% of the body weight loss and was provided in 6 equal volumes every 30 min during recovery. Blood and urine samples were collected at 60 min intervals during recovery for analysis. RESULTS: The 60 min run induced ~2% of body weight loss in all trials. During recovery, a greater fluid retention was found in CW trial compared with CE-H and CE-L trials (CE-H vs. CE-L vs. CW: 38.4 ± 5.2% vs. 36.1 ± 4.3% vs. 55.4 ± 3.8%, p < 0.01). Aldosterone level under CE-L trial was lower than CW trial at the 3rd hour of recovery (CE-L vs. CW: 262 ± 60 pg/mL vs. 355 ± 73 pg/mL, p < 0.05). After recovery, aldosterone concentrations were lower in both CE-H and CE-L trials than CW trial (CE-H vs. CE-L vs. CW: 228 ± 100 pg/mL vs. 211 ± 51 pg/mL vs. 333 ± 70 pg/mL, p < 0.05). By the end of the 1st and 2nd hour of recovery, the antidiuretic hormone in CE-L trial was lower than that in CW trial, but no difference was found between CE-H and CW trial. CONCLUSIONS: The ingested CW solution was retained greater than the CE-H and CE-L solutions during a 4-hour recovery after the 60 min run, which was partly caused by the higher concentration of aldosterone in the CW trial. The higher concentration of antidiuretic hormone may also account for the greater fluid retention, but further studies are still needed to clarify this issue.