Background: We aimed to determine the effect of resistance exercise intensity (% 1 repetition maximum-1RM) andvolume on muscle protein synthesis, anabolic signaling, and myogenic gene expression.Methodology/Principal Findings: Fifteen men (2161 years; BMI = 24.160.8 kg/m2) performed 4 sets of unilateral legextension exercise at different exercise loads and/or volumes: 90% of repetition maximum (1RM) until volitional failure(90FAIL), 30% 1RM work-matched to 90%FAIL (30WM), or 30% 1RM performed until volitional failure (30FAIL). Infusion of[ring-13C6] phenylalanine with biopsies was used to measure rates of mixed (MIX), myofibrillar (MYO), and sarcoplasmic(SARC) protein synthesis at rest, and 4 h and 24 h after exercise. Exercise at 30WM induced a significant increase above restin MIX (121%) and MYO (87%) protein synthesis at 4 h post-exercise and but at 24 h in the MIX only. The increase in the rateof protein synthesis in MIX and MYO at 4 h post-exercise with 90FAIL and 30FAIL was greater than 30WM, with nodifference between these conditions; however, MYO remained elevated (199%) above rest at 24 h only in 30FAIL. There wasa significant increase in AktSer473 at 24h in all conditions (P = 0.023) and mTORSer2448 phosphorylation at 4 h post-exercise(P = 0.025). Phosporylation of Erk1/2Tyr202/204, p70S6KThr389, and 4E-BP1Thr37/46 increased significantly (P,0.05) only in the30FAIL condition at 4 h post-exercise, whereas, 4E-BP1Thr37/46 phosphorylation was greater 24 h after exercise than at rest inboth 90FAIL (237%) and 30FAIL (312%) conditions. Pax7 mRNA expression increased at 24 h post-exercise (P = 0.02)regardless of condition. The mRNA expression of MyoD and myogenin were consistently elevated in the 30FAIL condition.Conclusions/Significance: These results suggest that low-load high volume resistance exercise is more effective in inducingacute muscle anabolism than high-load low volume or work matched resistance exercise modes.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Agricultural and Biological Sciences(all)