Background/Objective: 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. Methods: Ten young men aged 20.7±1.4 years with an average VO2max of 60.7mL/kg/min ran for 60 minutes at 65% VO2max on three occasions followed by 4 hours, recovery. During recovery, the participants consumed either CE solution with 66g/L carbohydrate (CHO), or CE plus whey protein solution (CW trial, 44g/L CHO, 22g/L whey), or CE plus casein protein solution (CC trial, 44g/L CHO, 22g/L casein); the solutions were matched for energy and electrolyte content. Results: 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±378mL vs. 1005±214mL vs. 1256±413mL; 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. Conclusion: 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.
Li, L., Wong, S. H. S., & Sun, F. H. (2015). Effects of protein addition to carbohydrate-electrolyte solutions on postexercise rehydration. Journal of Exercise Science and Fitness, 13(1), 8–15. https://doi.org/10.1016/j.jesf.2014.11.001