Effect of whey protein in carbohydrate-electrolyte solutions on post-exercise rehydration

Rapid and effective rehydration after prolonged endurance exercise is very important to replenish sweat loss during exercise. Carbohydrate-electrolyte (CE) solutions have been widely used for post-exercise rehydration. Recently, the addition of whey protein to CE solutions has been suggested to be more effective in rehydration than traditional CE solutions. However, it is still unclear whether the dosage of whey protein in solutions will result in different effects on post-exercise rehydration. PURPOSE: To investigate the effect of whey protein in CE solutions on post-exercise rehydration. METHODS: Ten males (age 22.3±1.6 year, body mass 65.5±5.6 kg, VO₂mₐₓ 60.4±5.7 ml/kg/min) ran for 60min at 65% VO2max on 4 occasions in a randomized crossover study design, separated by at least 7 days. During the 4 hour recovery period post-exercise, the subjects ingested either a CE solution, CE + high whey protein (CW-H) solution (protein:CHO = 1:1), CE + medium whey protein (CW-M) solution (protein:CHO = 1:2), or CE + low whey protein (CW-L) solution (protein:CHO = 1:3) equal to 150% of the body mass loss. The solutions were matched for energy density (264 kcal/L) and electrolytes content (Na⁺: 21 mmol/L; K⁺: 3.3 mmol/L), and were consumed in 6 equal volumes at 30min intervals during the recovery. Blood and urine samples were collected before and after exercise, as well as during the recovery. RESULTS: Subjects lost ~2% of their pre-exercise body weight in all trials. Total urine output after recovery was greater in CE trial than that in CW-M and CW-H trials (1269±390 vs. 1068±419 & 888±279 ml, p<0.05). The total fluid retention was greater after ingestion of CW-M and CW-H than CE and CW-L solutions (51.2±18.0% &. 56.5±13.2% vs. 40.1±19.5% & 43.4±16.1%, p<0.05). A lower urine specific gravity concentration and urine osmolality was found by the 4th hour in CE trial compared with the other three trials (p<0.05). No difference was found in the changes of plasma volume among the four trials during recovery. CONCLUSIONS: During a 4 hour recovery after the 60 min run, the CE solution with medium or high whey protein was more effective for rehydration when compared to the CE or CE with low whey protein.