Effects Of Sports Drinks Containing Different Components On Fluid Balance During Endurance Training

Purpose: To compare and evaluate the effects of sport drinks with various compositions on water-electrolyte balance and acid-alkaline balance during endurance training, providing guidance to athletes and coaches when choosing more appropriate and efficient sports drinks in endurance trainings and competitions.Method: Ten male athletes specializing in endurance events were recruited in this study. Three types of sport drink from the list of "Nutrition products list for national teams" were selected. The powder of these sports drinks mainly contained Low Molecular Carbohydrate(oligosaccharides, L-CHO), High Molecule Carbohydrate(hydrolyzed starch,H-CHO) and whey protein powder with carbohydrate(CHO-Pro, CHO:Pro=4:1). All drinks were diluted using pure water so that the experimental solution has carbohydrate concentration of 8%, a placebo-controlled solution was also used by adding Pla to the pure water.The exercise intensity was determined in the pilot test, where maximum oxygen intake was measured in endurance exercises. Randomized double-blind crossover method was used in the formal experiment. Formal experiment included four stages, each stage had 1 day of exercise test and 7 days of rest. On the days of exercise test, subjects ate the standard breakfast, then took 1 hour rest. After that, subjects started cycling test with intensity of 70% VO2 max, subjects were required to cycle at the cadence of 60 rpm for 1 hour. The solution was served with 1.8mL/kg at the 0, 15, 30, and 45 minute.At 0, 30, and 60 minutes, venous blood samples was collected. At the beginning and the end of the test, urine was collected. During the 30 minutes after the cycling test, solution was provided with the quantity of 10 m L/kg. At noon, subjects ate standard lunch. The second test started 6 hours after the first test, subjects were asked to cycle till exhaustion, the cycling duration was recorded. The same nutritious solution was provided as the first test. The RPE scale was used to asses fatigue level of the subject every 15 minutes. Venous blood and urine was collected.Results:(1) For all groups, bodyweight was significantly decreased, and plasma osmotic pressure and total plasma protein were significantly increased after exercise compared to resting state. Urine osmolality was similar prior and after the test, however, it was significantly higher in H-CHO group compared to Pla(control) group.(2) Na+ and Cl- in blood serum was similar prior and after the test. K+ in blood serum was significantly higher during and after the test compared to resting state. Na+ and Cl- in urine was similar prior and after the test. Cl- was significantly lower in H-CHO group compared to Pla group. K+ in urine was significantly decreased after the test.(3) The lactic acid increased significantly after the test, pH value was similar prior and after the test.(4) There was no significant differnce observed among the completoin times of exercise test in four groups.Conclusion:(1) L-CHO compared to other sports drinks has better function in maintaining water-electrolyte balance.(2) Supplement has no effect on lactic acid or pH value throughout the 1 hour endurance exercise.(3) Supplement has no effect on fitness test result.