According to the ISSN paper, leucine improves protein synthesis through mTOR stimulation, hVpS34 and calcium-related proteins, not during exercise, but after exercise. This effect can limit the excessive activation of NF-κB, attenuate and control inflammation, and its effects include delayed-onset muscle soreness. In fact, branched chain amino acids and other sulfur-containing amino acids, such as taurine, can reduce the damage to DOMS and muscles caused by eccentric exercise.
It is recommended to take BCAA before, during and after exercise. In order to optimize the total training fitness, you can consider taking no less than 45 mg/kg/day of leucine and no less than about 22.5 mg/kg/day of isoleucine and valine within 24 hours.