Document Type


Publication Date

Summer 6-2006


Exercise Science


The purpose of this study was to determine whether branched-chain amino acid (BCAA) supplementation attenuates indirect indicators of muscle damage, lowers ratings of perceived exertion, and improves aerobic performance as compared to an isocaloric, carbohydrate (CHO) beverage or a non-caloric placebo beverage. Nine, untrained males (VO2 max 36.26 2.23 ml/kg/min) performed three 90-minute cycling bouts at 55% VO2 max followed by a 15-minute time trial. Metabolic data was collected every 15 minutes during the steady-state ride, and indirect muscle damage markers were assessed pre, post, 4-hours, 24-hours, and 48-hours post-exercise. Pre and post-exercise concentrations of the BCAA and glucose were also recorded. All blood markers were adjusted for plasma volume shifts.There were no differences in dietary intake between trials for 3 days prior to exercise. Creatine kinase concentrations were significantly lower after the BCAA trial as compared to the placebo trial at 4, 24, and 48-hours post-exercise, as well as the CHO beverage at 24-hours post-exercise. Creatine kinase was lower in the CHO trial at the 24- and 48-hour time points as compared to the placebo trial. Lactate dehydrogenase concentrations were elevated in the placebo trial at 4-hours as compared to the BCAA trial. As compared to the alternate trials, ratings of perceived soreness were lower at 24-hours post-exercise, leg flexion torque was higher at the 48-hour time point, and plasma concentrations of the BCAA were elevated following the BCAA trial. Time-trial performance was improved in the CHO trial, and ratings of perceived exertion were lower at 75 and 90-minutes of exercise in the BCAA trial as compared to the placebo trial. There were no significant condition x time differences for leg extension torque, VO2, ventilation, heart rate, RER, or energy expenditure. In addition, there was no order effect for creatine kinase, lactate dehydrogenase, leg flexion/extension torque, ratings of perceived soreness, or time trial performance. The present data suggest that BCAA supplementation attenuates muscle damage during prolonged endurance exercise in unfit, college-aged males, but does not affect time trial performance. CHO ingestion improves time trial performance and attenuates post-exercise creatine kinase levels at 24-hours post-exercise as compared to a placebo beverage.


A dissertation submitted to the Department of Food, Nutrition, and Exercise Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy, The Florida State University College of Human Sciences. Degree awarded Summer Semester 2006.


Florida State University



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