The Effect of Drinking Skim Milk, Soy Milk and Water on Rehydration and Exercise Performance in Young Trained Females

The aim of this study was to compare the effects of drinking skim milk, soy milk, and water on fluid balance, rehydration and time to exhaustion during aerobic exercise. Eight trained females (age 21.37±0.71 years, BMI 22.06±1.42 Kg.m-2, VO2max 43.09±1.83 ml.kg-1.min-1) randomly assigned. The subjects ran on a treadmill at 75% of maximum heart rate for 20 minutes. This process continued for each subject until approximately 1.8±0.17% of reduction in body weight. Following that, subjects consumed one of the drinks randomized crossover design. The amount of consumed liquid was about 150% of the lost weight. Urine volume and urine specific gravity were measured after collecting urine samples. After the end of tree hours recovery, Bruce protocol was performed to evaluate exercise performance. The total volume of urine was significantly reduced in both milk and soy milk trials compared to water trial (P<0.05). Furthermore, the net fluid balance in these two trials was significantly positive compared to water trial (P<0.05) and the time to exhaustion was also longer than water trial (P<0.05). However, there was no significant difference between these two trials, milk and soy milk, in these variables (P>0.05). Therefore, drinking milk and soy milk led to better rehydration and fluid balance after exercise, which is associated with improved exercise performance.