Effects of protein addition to carbohydrate-electrolyte solutions on postexercise rehydration

This study aimed to examine the effects of the addition of whey or casein protein, the two major proteins in milk, to carbohydrate-electrolyte (CE) solutions on postexercise rehydration.

Ten young men aged 20.7 ± 1.4 years with an average VO_2max of 60.7 mL/kg/min ran for 60 minutes at 65% VO_2max on three occasions followed by 4 hours' recovery. During recovery, the participants consumed either CE solution with 66 g/L carbohydrate (CHO), or CE plus whey protein solution (CW trial, 44 g/L CHO, 22 g/L whey), or CE plus casein protein solution (CC trial, 44 g/L CHO, 22 g/L casein); the solutions were matched for energy and electrolyte content.

The participants lost 2.36 ± 0.32% of their pre-exercise body weight after the exercise. Total urine output after recovery was greater in the CE and CC trials than CW trial (CE vs. CW vs. CC: 1184 ± 378 mL vs. 1005 ± 214 mL vs. 1256 ± 413 mL; p < 0.05). Fluid retention after ingestion of CW solution was greater than CE and CC solutions (CE vs. CW vs. CC: 46.9 ± 16.5% vs. 54.9 ± 9.2% vs. 45.8 ± 17.3%; p < 0.05). Lower urine specific gravity and urine osmolality were observed by the end of recovery in the CE trial compared with CW trial (p < 0.05). No difference was found in the changes in plasma volume in all trials.

These results suggest that during the 4 hours' recovery after a 60-minute run, the CW solution was more effective for rehydration compared with the CE or CC solution.