Additional Effects of Taurine on the Benefits of BCAA Intake for the Delayed-Onset Muscle Soreness and Muscle Damage Induced by High-Intensity Eccentric Exercise

BCAA catabolism in skeletal muscle is regulated by the branched-chain alpha-keto acid dehydrogenase (BCKDH) complex, located at the second step in the BCAA catabolic pathway. The activity of the BCKDH complex is regulated by a phosphorylation/dephosphorylation cycle. Almost all of BCKDH complex in skeletal muscle under normal and resting conditions is in an inactive/phosphorylated state, which may contribute to muscle protein synthesis and muscle growth. Exercise activates the muscle BCKDH complex, resulting in enhanced BCAA catabolism. Therefore, exercise may increase the BCAA requirement. It has been reported that BCAA supplementation before exercise attenuates the breakdown of muscle proteins during exercise in humans and that leucine strongly promotes protein synthesis in skeletal muscle in humans and rats, suggesting that a BCAA supplement may attenuate muscle damage induced by exercise and promote recovery from the damage. We have examined the effects of BCAA supplementation on delayed-onset muscle soreness (DOMS) and muscle fatigue induced by squat exercise in humans. The results obtained showed that BCAA supplementation prior to squat exercise decreased DOMS and muscle fatigue occurring for a few days after exercise. These findings suggest that BCAAs may be useful for muscle recovery following exercise.

The purpose of this study was to examine the role of branched-chain amino acid (BCAA) supplementation during recovery from intense eccentric exercise. Twenty-four non-weight-trained males were assigned to one of two groups: one group (supplementary, SUP) ingested BCAA beverages (n = 12); the second group (placebo, PLA) ingested artificially flavored water (n = 12). Diet was controlled throughout the testing period to match habitual intake. The eccentric exercise protocol consisted of 12 x 10 repetitions of unilateral eccentric knee extension exercise at 120% concentric one repetition maximum. On the day of the exercise, supplements were consumed 30 min before exercise, 1.5 h after exercise, between lunch and dinner, and before bed. On the following 2 d, four supplements were consumed between meals. Muscle soreness, muscle function, and putative blood markers of muscle damage were assessed before and after (1, 8, 24, 48, and 72 h) exercise. Muscle function decreased after the eccentric exercise (P < 0.0001), but the degree of force loss was unaffected by BCAA ingestion (51% +/- 3% with SUP vs -48% +/- 7% with PLA). A decrease in flexed muscle soreness was observed in SUP compared with PLA at 48 h (21 +/- 3 mm vs 32 +/- 3 mm, P = 0.02) and 72 h (17 +/- 3 mm vs 27 +/- 4 mm, P = 0.038). Flexed muscle soreness, expressed as area under the curve, was lower in SUP than in PLA (P = 0.024). BCAA supplementation may attenuate muscle soreness, but it does not ameliorate eccentric exercise-induced decrements in muscle function or increases in reputed blood markers of muscle damage, when consumed before exercise and for 3 d after an eccentric exercise bout.