Low-load high volume resistance exercise stimulates muscle protein synthesis more than high-load low volume resistance exercise in young men

Abstract

Background: We aimed to determine the effect of resistance exercise intensity (%1 repetition maximum-1RM) and volume on muscle protein synthesis, anabolic signaling, and myogenic gene expression.

Methodology/principal findings: Fifteen men (21+/-1 years; BMI=24.1+/-0.8 kg/m2) performed 4 sets of unilateral leg extension 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 rest in 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 rate of protein synthesis in MIX and MYO at 4 h post-exercise with 90FAIL and 30FAIL was greater than 30WM, with no difference between these conditions; however, MYO remained elevated (199%) above rest at 24 h only in 30FAIL. There was a 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 the 30FAIL condition at 4 h post-exercise, whereas, 4E-BP1Thr37/46 phosphorylation was greater 24 h after exercise than at rest in both 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 inducing acute muscle anabolism than high-load low volume or work matched resistance exercise modes.

Figure 1. Fasted-state mixed (A), myofibrillar (B), and sarcoplasmic (C) protein synthesis (FSR) at rest and following resistance exercise.

Capital letter indicates a mean that is significantly different from rest, P<0.05. *Significantly different from 30WM within that time point, P<0.05. †Significantly different from 90FAIL within that time point, P<0.05. ‡Significantly different from 24h post within group. Values are means ± SEM.

Figure 2. Akt (A), Erk1/2 (B), mTOR (C) following resistance exercise.

Capital letter indicates a mean that is significantly different from rest, P<0.05. *Significantly different from 30WM within that time point, P<0.05. †Significantly different from 90FAIL within that time point. #Significant main effect for time, P<0.05. Data are expressed as fold change from rest. Values are means ± SEM.

Figure 3. p70S6K (A), 4E-BP1 (B), and eEF2 (C) following resistance exercise.

Capital letter indicates a mean that is significantly different from rest, P<0.05. *Significantly different from 30WM within that time point, P<0.05. †Significantly different from 90FAIL within that time point, P<0.05. #Significant main effect for time, P<0.05. Data are expressed as fold change from rest. Values are means ± SEM.

Figure 4. Relationship between myofibrillar protein synthesis and the extent of phosphorylation of 4E-BP1 (Thr 37/46) at 24 hours following resistance exercise.

There was a significant correlation (P = 0.049) between the degree of phosphorylation (fold-change from basal) and myofibrillar protein synthesis (FSR, %/hr).

Figure 5. Pax7 (A), MyoD (B), myogenin (C) mRNA expression in skeletal muscle 24 hours following resistance exercise.

Data are expressed as fold change from rest. Data are normalized to GAPDH and reported as mean ± SEM. *Significantly different from rest, P<0.05. †Significantly different from 30WM.