A 7-day oral supplementation with branched-chain amino acids was ineffective to prevent muscle damage during a marathon

The aim of this study was to determine the effectiveness of a 7-day oral supplementation with branched-chain amino acids (BCAA) to prevent muscle damage during a marathon. Forty-six experienced runners were randomly divided into two groups, one with BCAA supplementation (n = 25, supplemented with 5 g day(-1) of powdered 1:0.5:0.5 leucine:isoleucine:valine, during the 7 days prior to the competition) and the other as a control group (n = 21, supplemented with an isocaloric placebo). Before the marathon race and within 3 min of finishing, leg muscle power was measured with a maximal countermovement jump and a urine sample was obtained. During the race, running pace was measured by means of a time-chip. Myoglobin concentration was determined in the urine samples as an indirect marker of muscle damage. A visual analog scale (0-10 points) was used to assess leg muscle pain during the race. In the BCAA group, the mean running pace during the marathon was similar to the control group (3.3 +/- A 0.4 vs. 3.3 +/- A 0.5 m s(-1), respectively, 0.98). The pre- to post-race reduction in muscle power was similar in both BCAA and control groups (-23.0 +/- A 16.1 vs. -17.3 +/- A 13.8 %, P = 0.13). Post-race urine myoglobin concentration was similar in both BCAA and control groups (5.4 +/- A 7.5 vs. 4.5 +/- A 8.6 mu g mL(-1), P = 0.70). Finally, there were no differences between groups in the perceived muscle pain during the race (6 +/- A 1 vs. 5 +/- A 1 points, P = 0.80). A 7-day supplementation of BCAA (5 g day(-1)) did not increase the running performance during a marathon. Furthermore, BCAA supplementation was ineffective to prevent muscle power loss, muscle damage or perceived muscle pain during a marathon race.