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PURPOSE: Branched Chain Amino Acids (BCAA) have been theorized to delay the onset of fatigue. When BCAA concentration is low, serotonin precursors cross the blood-brain barrier more easily and are converted into serotonin which has been found to depress motor neuron excitability. By ingesting BCAA's, the ratio of Serotonin precursors to BCAAs is reduced. The aim of this study was to observe the effects BCAA’s have on central fatigue when in a glycogen reduced state during an incremental exercise that results in volitional exhaustion. METHODS: 11 college-aged untrained individuals participated in a single-blind, within-subject, counter-balanced design. Subjects underwent a glycogen depletion protocol (GDP) consisting of a 20-minute cycling bout with a resistance that elicited a heart rate of 65% of VO2max and 3, 2-minute interval cycling bouts with 1.7kg of resistance while they maintained a cadence of 50rpm followed by an incremental volitional fatigue protocol which involved cycling with an initial 1kg of resistance with .5kg added every 2 minutes while they maintained a constant rate of 40 (± 5) rpms. The test was terminated when the subject was unable to maintain the cycling cadence. Subjects completed a total of two trials (BCAA and placebo) with 7 days between trials. RESULTS: A Repeated Measures (RM) ANOVA showed that there were no significant differences (p<0.05) between time (496.1 ± 243.6s vs. 550.3 ± 333.1s) and total work (90593 ± 38813.6J vs. 103544.8 ± 57536.5J) for the 20-minute GDP nor were there differences between time (266.5 ± 54.3s vs. 263.1 ± 59.4s) and total work (58168.5 ± 15538.0J vs. 57162.1 ± 17000.7J) for the 3, 2-minute interval GDP compared between conditions (BCAA vs Control, mean±SD). Another RM ANOVA showed no differences (p<0.05) between time (913.9±173.8s vs. 925.4±247.5s), total work (101718.8 ± 34811.3J vs. 105170.5 ± 48652.5J), and RPE (15.52 ± 1.5 vs. 16.7 ± 1.5) compared between conditions (BCAA vs Control, mean±SD) for the Volitional Protocol. A linear regression showed a significant correlation for RPE vs. Time for the control condition (r= 0.755),( p < .01) but a non-significant correlation for RPE vs. Time for the BCAA condition (r=0.504, p = 0.25). CONCLUSION: There were no significant differences (p<0.05) between our variables for placebo and BCAA conditions. The difference in correlation for RPE vs. Time between the two conditions may indicate that BCAA have an effect on fatigue. We can conclude that work was successfully controlled based on the similarity of total work for the GDP. More research needs to be done in the area of BCAA’s to determine their relationship to fatigue.

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