Effects of sports drinks with different molecular weight carbohydrates on rehydration during endurance exercise: a comparative study.

Background: The aim of this study was to compare the impacts of low-molecular-weight (LMW) and high-molecular-weight (HMW) carbohydrate (CHO) sports drinks on rehydration during endurance exercise.

Methods: Ten middle- and long-distance running athletes were selected in a randomized, double-blind, cross-over design. One day before the experiment, a pre-experiment was performed to determine the VO2peak. The formal experiment consisted of a two-stage exercise test. In the first test, participants rode an electrically braked cycle ergometer for 1 hour with an intensity of 70%VO2peak and were supplemented with three kinds of sports drinks, namely, LMW CHO (oligosaccharides), HMW CHO (Vitargo), and placebo (PLA), at 1.8 mL/kg·bw every 15 minutes. Venous blood, capillary blood, and urine were collected during exercise. The second test was conducted 6 hours after the first test and employed an intensity of 75%VO2peak and the same rehydration strategy. The rate of perceived exertion (RPE) was recorded every 15 minutes until exhaustion, and the time to exhaustion (TTE) was recorded.

Results: The percentage of body weight loss before and after exercise was significantly lower in the LMW group than in the HMW group (P<0.05). The serum or urine Na⁺, K⁺, and Cl^- concentrations did not significantly differ among the groups (P>0.05). No significant differences in plasma osmolarity, urine osmolarity, lactic acid, blood pH, or exercise exhaustion time were found among the groups (P>0.05).

Conclusions: Sports drinks containing LMW CHO were better at maintaining hydration than those containing HMW CHO. Sports drinks with different molecular weights of CHO had no significant effect on athletic performance or blood pH.