On trial days, the subjects in the fasting state reported to the laboratory at 0830 h and then ingested a jelly-type food (200 g in weight containing 100 kcal from sugar) (Otsuka Pharmaceutical) at 0900 h and, 30 min later, the BCAA or placebo solution. The squat exercise session commenced ~15 min after ingestion of the test solution. BCAA (or placebo) ingestion occurred prior to the exercise trial because it has been reported that (1) BCAA supplementation before exercise attenuated muscle protein breakdown (25), (2) postexercise muscle protein synthesis was greater when essential amino acids were consumed before exercise, rather than after (28), (3) in a separate preliminary study, we found that plasma BCAA concentrations were elevated within 15 min and peaked 30 min after ingestion when the 5 g of BCAA mixture were ingested, and (4) dietary BCAAs may affect energy metabolism during exercise (29). Muscle soreness before and after exercise and for the following 4 d (from the second through the fifth day) was evaluated while sitting using a visual-analogue scale consisting of a 10-cm line with "no pain" printed at one end and "extremely sore" at the other (30). Muscle fatigue was evaluated at the same time using a visual-analogue scale consisting of a 10-cm line with "no fatigue" printed at one end and "extreme fatigue" at the other. The subject was instructed to make a mark on the line indicating the degree of muscle soreness and muscle fatigue he/she felt. Informed, written consent was obtained from all subjects before participating in the study. The study protocol was approved by the human research review committee of the Nagoya University School of Medicine. (...)
The results obtained in this preliminary study indicate that the ingestion of 5 g of BCAAs before exercise can reduce DOMS and muscle fatigue for several days after exercise. The mechanisms that underlie these BCAA effects have not yet been examined. However, one possibility is that BCAA may attenuate exercise-induced protein breakdown, while leucine may stimulate muscle protein synthesis. If the finding is substantiated, the results could support the usefulness of BCAA in muscle recovery from exercise. Further studies are required to elucidate the mechanisms responsible for the effects of BCAA supplementation.
