Effects of sucrose or caffeine ingestion on running performance and biochemical responses to endurance running

To elucidate the effects of sucrose or caffeine ingestion on metabolic responses to prolonged exercise and on performance of a finishing spurt after the prolonged exercise, seven male physical education students performed four sets of 30 min running (62%-67% VO2 max) followed by progressive exhaustive running on a treadmill. Before each set, they took 350 ml solution containing either sucrose 23.8 g (97.5 kcal), caffeine 200 mg, or a placebo. The duration of the exhaustive running after sucrose, caffeine, or placebo ingestion was not significantly different. Exhaustion would possibly be attained not by depletion of muscle glycogen but by a decrease in the capacity of muscle cells to produce high tension for anaerobic metabolism. Total energy and energy from carbohydrate combusted during four sets of running were estimated at 1255 kcal and 810 kcal in the sucrose trial, 1271 kcal and 624 kcal in the caffeine trial, and 1248 kcal and 649 kcal in the placebo trial. Judging from the figures above, glycogen sparing during prolonged running seemed to be attained by sucrose ingestion but not by caffeine ingestion. The latter finding would be caused by lower intensity and a larger amount of ingested caffeine. In conclusion, performance of progressive exhaustive running following endurance running for 2 h could not be improved either by sucrose or caffeine ingestion. Glycogen sparing in the muscle, however, was suggested by sucrose ingestion but not by caffeine ingestion.