支鏈胺基酸增補對下坡跑後肌肉激素－irisin及肌肉損傷與合成指標之效應

Background: Studies had suggested that exercise-induced irisin may function as an exercise signal to facilitate muscle anabolism under muscle damage. It has been proven that branched-chain amino acids (BCAA) could attenuate muscle damage and promote protein synthesis after eccentric exercise. Besides, positive correlation has been found between BCAA and irisin level. Purpose: To examine the effects of BCAA supplementation on blood irisin levels, muscle damage and other muscle growth-related factors following downhill running. Methods: A total of 12 physically inactive young healthy men were recruited and completed two bouts of downhill running (-15°) at 70% V?O2max for 30 minutes with supplementation of either 100mg/ bodyweight of BCAA (BCAA) or placebo (PLA) 15 mins before, immediately after and 3h after running in a double-blinded, crossover design. A control trial (CON) with BCAA supplementation but exercise was carried out a week before the two running trials. Irisin, creatine kinase (CK), myostatin, IL-6, muscle soreness and maximal voluntary isometric contraction (MVIC) were measured at baseline, immediately, 3h, 24h and 48h after exercise during running trials and at baseline and 24h during control trial. A two-way (supplementation × time) repeated ANOVA were used for analyzing the collected data. Results: 1.time main effect of CK and MVIC: CK peaked at 24h 3h and 48h were higher than baseline and immediately after running. Baseline was lower than immediately after running. MVIC pealed at baseline, 48h was higher than 3h and immediately after running 2. VAS: at 3h and 24h, BCAA were lower than PLA. 3. irisin: no interaction. BCAA tended to be higher than CON at 24h. 4.myostatin: no interaction, immediately and 3h after running were higher than baseline. 5. IL-6: no interaction: IL-6 pealed at 3h and baseline was lower than immediately after running. 6. Change rate of irisin and myostain at 3h was significantly negatively correlated (r = -.436). Conclusion: A total of 300 mg/kg BCAA supplemented before and after downhill running improved VAS at 3h and 24h but didn’t affect muscle damage or muscle strength. Blood irisin levels did not increase after downhill running while myostatin increased immediately and 3h after running. Irisin was negatively correlated with myostatin after downhill running, but the mechanism or influences between them still needs further study.