Since blood flow is known to increase following resistance exercise, which also increases amino acid transport and uptake into muscle cells, it seems reasonable to assume that the greater amounts of muscle mass involved would result in increased amino acid uptake and a resulting increase in the post-workout protein requirement for maximal MPS stimulation. This led the authors to propose that 20-25 grams of whey protein may be insufficient to promote maximal recovery from whole-body resistance exercise.
Although the increased amount of muscle mass used during whole-body workouts may account for differences from previous studies arriving at the 20-25 gram number for maximal MPS, the authors note other possible explanations. One of those differences may be attributed to sample size, which was larger in the present study (n=30) than previous work which used 12 and 6 participants. This is further supported by the fact that significance of MPS differences was not observed within the low LBM or the high LBM groups, but combining the two groups (and thus, increasing statistical power) did lead to a significant difference. It is possible that previous studies with smaller sample sizes lacked that statistical power to detect subtle, but real trends in the data.
Another explanation for discrepancies could be the type of protein ingested. This is unlikely however, given that the previous studies arriving at the 20-25 gram number used different types of proteins and yet arrived at the same number. Therefore, even after accounting for possible confounders, results from the present study suggest that exercise involving greater amounts of muscle mass may increase protein requirements for maximal acute activation MPS. The authors sum up their conclusions in the paper: “It seems that the overall amount of muscle mass possessed by the individual is a less important determinant of the maximally effective dose of protein to ingest than the amount of muscle mass activated during exercise.”
Taking the results of this study at face value, the implication is that the amount of muscle mass used during a given training session may dictate post-workout protein requirements for maximal activation of MPS after training. Although more research is needed with larger experimental groups, the evidence is sufficient to suggest that those consuming only 20-25 grams protein after training may benefit from 40 grams. This brings about some more practical, less ‘academic’ considerations. To repair damaged muscle tissue after strenuous weight training and add new lean tissue as part of the adaptive process, a certain amount of high quality protein is required. In the big picture, it is important to get enough of said high quality protein. Getting ‘only enough’ is of less importance, assuming there are no underlying health issues or dietary restrictions that contraindicate the increased amount of protein. At the best, bumping up post-workout protein consumption from 25 to 40 grams may be helpful. At the worst, ‘excess’ protein is consumed: 60 extra kcals from 15 grams of additional protein will likely not disrupt even the most stringent of diets. Future research may determine how much protein is needed for different types of individuals in response to varying training methodologies.
Although more research is needed, the current study suggests that those consuming only 20-25 grams protein after training may achieve greater post-workout MPS with 40 grams.