Effect of milk protein addition to a carbohydrate–electrolyte rehydration solution ingested after exercise in the heat

The present study examined the effects of milk protein on rehydration after exercise in the heat, via the comparison of energy- and electrolyte content-matched carbohydrate and carbohydrate–milk protein solutions. Eight male subjects lost 1.9 (SD 0.2) % of their body mass by intermittent exercise in the heat and rehydrated with 150 % of their body mass loss with either a 65 g/l carbohydrate solution (trial C) or a 40 g/l carbohydrate, 25 g/l milk protein solution (trial CP). Urine samples were collected before and after exercise and for 4 h after rehydration. Total cumulative urine output after rehydration was greater for trial C (1212 (SD 310) ml) than for trial CP (931 (SD 254) ml) (P<0.05), and total fluid retention over the study was greater after ingestion of drink CP (55 (SD 12) %) than that after ingestion of drink C (43 (SD 15) %) (P,0.05). At the end of the study period, whole body net fluid balance (P<0.05) was less negative for trial CP (20.26 (SD 0.27) litres) than for trial C (20.52 (SD 0.30) litres), and although net negative for both the trials, it was only significantly negative after ingestion of drink C (P