Delayed onset muscle soreness (DOMS) is often caused by intense, unaccustomed exercise. Consuming protein with high essential amino acid (EAA) content has been known to support post-exercise muscle protein synthesis, but a recent study aimed to examine the effects of essential amino acid (EAA) supplementation on soreness and muscle damage after heavy eccentric training.
23 untrained men supplemented with EAAs (15g EAA + 15g sucrose) or a placebo (30g sucrose). They did 8 sets of 6 bench press reps with 4-second eccentrics. Supplements were consumed immediately post-workout, and for 6 days after. These subjects typically consumed about 1.2 g/kg/day of protein.
The researchers concluded that EAAs did not significantly attenuate increases in muscle damage biomarkers (CK or Mb). However, the stats aren’t presented very clearly, the figures show pretty notable differences, and a large number of subjects had very, very small peak CK and Mb responses, which is atypical. Overall, the muscle damage data should be interpreted very cautiously. Nonetheless, soreness values were not significantly affected.
The bottom line: When we look at the broader literature (including BCAA supplementation studies), there is reason to believe that supplementation with BCAAs or EAAs may modestly expedite recovery from extremely vigorous and unaccustomed bouts of exercise, especially in untrained subjects. However, as a lifter becomes more accustomed to their training style, the repeated bout effect should reduce their susceptibility to extremely high levels of acute muscle damage, especially with a well-designed training program. In addition, it seems likely that sufficient intake of complete proteins (or a properly diversified group of incomplete proteins) would supply plenty of BCAAs and EAAs. However, if an extreme exercise bout cannot be avoided for some reason, and optimal protein intake cannot be achieved, EAA supplementation might be the next best option for supporting recovery.