Relationship Between Resistance Exercise Volume and Muscle Protein Metabolism

Abstract

Resistance exercise volume is known as an important factor to stimulate muscle protein synthesis (MPS) and the mechanistic target of rapamycin complex 1 (mTORC1) signaling is considered to be involved in the mechanisms. However, the effects of relatively high-volume resistance exercise on mTORC1 signaling and MPS remain unclear. Thus, the purpose of this study was to investigate the relationship between resistance exercise volume and MPS using animal model of resistance exercise. Male Sprague-Dawley rats aged 11 weeks were subjected to resistance exercise, and gastrocnemius samples were obtained 6 h after performing 1, 3, 5, 10, or 20 sets of resistance exercise. Significant increase in p70S6K phosphorylation, a marker of mTORC1 activity, after resistance exercise was observed in all of exercise conditions tested, and the phosphorylation degree gradually increased with increasing number of resistance exercise sets. On the other hand, although resistance exercise increased MPS gradually with increasing sets of resistance exercise, the increase in MPS reached a plateau after 5 sets of resistance exercise, and no further increase in MPS was observed in response to additional resistance exercise sets. Therefore, the increase in MPS with increasing resistance exercise volume may be saturated independent of p70S6K phosphorylation.