Title : The Effect of Post - Exercise Milk Protein Intake on Rehydration of Children

Purpose: In adults, rehydration after exercise in the heat can be enhanced with a proteincontaining beverage; however, whether this applies to children remains unknown. This study examined the effect of milk protein intake on post-exercise rehydration in children. Method: Fifteen children (10-12 years) performed three exercise trials in the heat (34.4 ± 0.2 °C, 47.9 ± 1.1% relative humidity). In a randomized, counterbalanced crossover design, participants consumed iso-caloric and electrolyte-matched beverages containing 0-g (CONT), 0.76-g (LoPRO) or 1.5-g (Hi-PRO) of milk protein/100mL in a volume equal to 150% of their body mass (BM) loss during exercise. BM was then assessed over 4 h of recovery. Results: Fluid balance demonstrated a significant condition × time interaction (p = 0.012) throughout recovery; Hi-PRO was less negative than CONT at 2 h (p = 0.01) and tended to be less negative at 3 h (p = 0.07). Compared to CONT, beverage retention was enhanced by Hi-PRO at 2 h (p < 0.05). Conclusion: A post-exercise beverage containing milk protein can favourably affect fluid retention in children. Further research is needed to determine the optimal volume and composition of a rehydration beverage for complete restoration of fluid balance.