Proceedings of The Physiological Society

University of Manchester (2010) Proc Physiol Soc 19, C105

Oral Communications

Resistance exercise-induced increases in myofibrillar protein synthesis and p70S6K phosphorylation are greater after three sets versus one set in young men

N. A. Burd1, A. M. Holwerda1, K. C. Selby1, A. W. Staples1, N. Cain1, D. W. West1, S. K. Baker1, S. M. Phillips1

1. Kinesiology, McMaster University, Hamilton, Ontario, Canada.

The efficacy of single (1SET)-versus multiple-sets (i.e., 3 sets; 3SET) of resistance exercise in inducing gains in muscle size and strength are equivocal. We aimed to determine if any mechanistic differences exist between these two training paradigms by examining the response of myofibrillar protein synthesis (MPS) and anabolic signalling molecule phosphorylation following an acute bout of resistance exercise. Eight young recreationally resistance trained men (24±5 years, BMI= 25±4 kg m-2) were randomly assigned to performed unilateral leg extension exercise at 70% concentric 1 repetition maximum (1RM) until volitional fatigue for 1SET or 3SET. Biopsies from the vastus lateralis were taken at rest, 5 h, 24 h, 29 h post-exercise in the fasted- and fed- (20g of whey protein isolate) states. A primed- (2.0 µmol/kg) continuous (0.05 µmol kg-1 min-1) infusion of [ring-13C6] phenylalanine was utilized to measure MPS by gas-chromatography-combustion-mass spectrometry using [ring-13C6] phenylalanine enrichment in the intracellular free amino acid pool as the precursor. Phosphorylation of p70 ribosomal S6 kinase (p70S6K) and eukaryotic translation initiation factor 2B epsilon (eIF2Bε) were measured using Western blot analysis. Repetitions performed were 14±2 for 1SET and 14±3, 11±2, 9±3 for sets 1, 2, 3 respectively for 3SET. Fed-state MPS was elevated above rest to a similar extent at 5h for 1SET (~2.2-fold) and 3SET (~2.8-fold; P<0.001); however, this response was sustained only in 3SET at 29h post-exercise (2.0-fold above rest; P=0.007). Similarly, resistance exercise induced a 61±33% and 64±26% increase above rest at 5h post-exercise in p70S6K phosphorylation for 1SET and 3SET, respectively (P=0.037). Interestingly, p70S6K phosphorylation returned to rest at 24 h, but feeding stimulated phosphorylation of p70S6K above rest only in 3SET at 29 h (P=0.013). Exercise with 3SET, but not 1SET, also decreased phosphorylation, indicative of activation, of eIF2Bε by 37±9% at 5 h post-exercise (P<0.05). These data suggest that multiple-sets of resistance exercise are more anabolic than a single-set and may lead to greater increases in protein accretion in healthy young men. The mechanisms for the changes in MPS we observed are unclear but appear to involve p70S6K. These data provide insight for the development of exercise prescriptions to maximize muscle growth and/or attenuate muscle loss.

Where applicable, experiments conform with Society ethical requirements