Effects of preexercise candy bar ingestion on glycemic response, substrate utilization, and performance

This study examined the effects of preexercise candy bar ingestion on glycemic response, substrate utilization, and performance in 8 trained male cyclists. The cyclists randomly ingested one large milk chocolate bar (1CB), two large milk chocolate bars (2CB), or a placebo (P) 30 min prior to a 90-min cycle ride at 70% VO2max followed by a 33-W increase every 2 min until exhaustion (approximately 10 min). Glucose decreased after 15 min of exercise but returned to preexercise values by 30 min of exercise. Glucose concentration for 2CB was significantly higher than for P and 1CB at exhaustion. Insulin concentration increased in response to 1CB and 2CB and returned to preexercise values within 15 min of exercise. No significant differences were noted for free fatty acid (FFA) concentrations, lactate concentrations, respiratory exchange ratio, total carbohydrate oxidation, or estimated fat and carbohydrate oxidation rates. Time to exhaustion was similar among the groups. The results suggest that the transient lowering of blood glucose observed with preexercise milk chocolate bar ingestion 30 min prior to exercise may not cause major metabolic perturbations that impair athletic performance in trained athletes performing moderately intense cycle exercise.