Protein supplementation does not alter intramuscular anabolic signaling or endocrine response after resistance exercise in trained men

Nutr Res. 2015 Nov;35(11):990-1000. doi: 10.1016/j.nutres.2015.09.006. Epub 2015 Sep 10.


The mammalian/mechanistic target of rapamycin complex 1 (mTORC1) signaling pathway appears to be the primary regulator of muscle protein synthesis. A variety of stimuli including resistance exercise, amino acids, and hormonal signals activate mTORC1 signaling. The purpose of this study was to investigate the effect of a protein supplement on mTORC1 signaling following a resistance exercise protocol designed to promote elevations in circulating hormone concentrations. We hypothesized that the protein supplement would augment the intramuscular anabolic signaling response. Ten resistance-trained men (age, 24.7 ± 3.4 years; weight, 90.1 ± 11.3 kg; height, 176.0 ± 4.9 cm) received either a placebo or a supplement containing 20 g protein, 6 g carbohydrates, and 1 g fat after high-volume, short-rest lower-body resistance exercise. Blood samples were obtained at baseline, immediately, 30 minutes, 1 hour, 2 hours, and 5 hours after exercise. Fine-needle muscle biopsies were completed at baseline, 1 hour, and 5 hours after exercise. Myoglobin, lactate dehydrogenase, and lactate concentrations were significantly elevated after resistance exercise (P < .0001); however, no differences were observed between trials. Resistance exercise also elicited a significant insulin, growth hormone, and cortisol response (P < .01); however, no differences were observed between trials for insulin-like growth factor-1, insulin, testosterone, growth hormone, or cortisol. Intramuscular anabolic signaling analysis revealed significant elevations in RPS6 phosphorylation after resistance exercise (P = .001); however, no differences were observed between trials for signaling proteins including Akt, mTOR, p70S6k, and RPS6. The endocrine response and phosphorylation status of signaling proteins within the mTORC1 pathway did not appear to be altered by ingestion of supplement after resistance exercise in resistance-trained men.

Keywords: Amino acids; Hormones; Leucine; Sports nutrition; mTOR pathway; mTORC1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Dietary Proteins / pharmacology*
  • Dietary Supplements*
  • Human Growth Hormone / blood
  • Human Growth Hormone / drug effects
  • Humans
  • Hydrocortisone / blood
  • Insulin / blood
  • Insulin-Like Growth Factor I / drug effects
  • Male
  • Muscle Proteins / blood*
  • Muscle Proteins / drug effects
  • Muscle, Skeletal / drug effects*
  • Resistance Training*
  • Signal Transduction / drug effects*
  • TOR Serine-Threonine Kinases / blood
  • TOR Serine-Threonine Kinases / drug effects
  • Testosterone / blood
  • Young Adult


  • Dietary Proteins
  • Insulin
  • Muscle Proteins
  • Human Growth Hormone
  • Testosterone
  • Insulin-Like Growth Factor I
  • MTOR protein, human
  • TOR Serine-Threonine Kinases
  • Hydrocortisone