The Effects Of Three Pre-exercise Meals On Long And Short-term Submaximal Cycling Endurance Exercise

Abstract

PURPOSE: To determine the effects of pre-exercise meals on blood and cardiorespiratory variables during long-term and short-term submaximal endurance cycling. METHODS: Eighteen endurance trained males, ages of 18 - 35 years, participated in this study examining the effects of 200 iso-caloric meals (300 mL) of glucose, whole milk, and an artificially flavored placebo after an overnight fast and 2-day diet high (>60%) in complex carbohydrates fed 30 minutes prior to separate rides at 55% of VO2max for 120 minutes, followed by a 30 minute rest, and a short high intensity ride to exhaustion at 80% of VO2max. Subjects were healthy and each paid $100 for their participation. Variables measured were blood glucose, glycerol, free fatty acids, and lactate, respiratory exchange ratio, heart rate, rating of perceived exertion, and time to exhaustion. Data were analyzed using a two-way repeated measures ANOVA. Significant differences (p < 0.05) were tested using a Bonferroni post hoc test. RESULTS: Only the means of the free fatty acids were significantly different between the long ride trials (p <.007) with milk and glucose significantly blunting the rise in free fatty acids with exercise. Over time in the long ride free fatty acids, glycerol, and heart rate increased significantly and glucose, lactate, and respiratory exchange ratio decreased significantly. On the short rides there were no significant differences between any of the variables (p < 0.05). While the differences were not significant, time to exhaustion for the carbohydrate meal was 18% longer than milk and 20% longer than the placebo. CONCLUSIONS: These results demonstrate that, following an overnight fast, a 200 kilocalorie meal prior to endurance exercise will not make a difference in time to exhaustion if it is a carbohydrate or whole milk meal. Additionally, a whole milk meal will blunt the free fatty acid response during endurance exercise similar to that of a carbohydrate only meal.