Resistance exercise‐induced increases in putative anabolic hormones do not enhance muscle protein synthesis or intracellular signalling in young men
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abstract
We aimed to determine whether exercise‐induced elevations in systemic concentration of testosterone, growth hormone (GH) and insulin‐like growth factor‐1 (IGF‐1) enhanced post‐exercise myofibrillar protein synthesis (MPS) and phosphorylation of signalling proteins important in regulating mRNA translation. Eight young men (20 ± 1.1 years, BMI = 26 ± 3.5 kg m−2) completed two exercise protocols designed to maintain basal hormone concentrations (low hormone, LH) or elicit increases in endogenous hormones (high hormone, HH). In the LH protocol, participants performed a bout of unilateral resistance exercise with the elbow flexors. The HH protocol consisted of the same elbow flexor exercise with the contralateral arm followed immediately by high‐volume leg resistance exercise. Participants consumed 25 g of protein after arm exercise to maximize MPS. Muscle biopsies and blood samples were taken as appropriate. There were no changes in serum testosterone, GH or IGF‐1 after the LH protocol, whereas there were marked elevations after HH (testosterone, P < 0.001; GH, P < 0.001; IGF‐1, P < 0.05). Exercise stimulated a rise in MPS in the biceps brachii (rest = 0.040 ± 0.007, LH = 0.071 ± 0.008, HH = 0.064 ± 0.014% h−1; P < 0.05) with no effect of elevated hormones (P= 0.72). Phosphorylation of the 70 kDa S6 protein kinase (p70S6K) also increased post‐exercise (P < 0.05) with no differences between conditions. We conclude that the transient increases in endogenous purportedly anabolic hormones do not enhance fed‐state anabolic signalling or MPS following resistance exercise. Local mechanisms are likely to be of predominant importance for the post‐exercise increase in MPS.
