title: Resistance exercise-induced increases in putative anabolic hormones do not enhance muscle protein synthesis or intracellular signalling in young men.
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.
authors.affiliation: Exercise Metabolism Research Group, Department of Kinesiology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada.
authors.forename: Daniel W D
authors.initials: DW
authors.lastname: West
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Kujbida
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Moore
authors.forename: Philip
authors.initials: P
authors.lastname: Atherton
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Burd
authors.forename: Jan P
authors.initials: JP
authors.lastname: Padzik
authors.forename: Michael
authors.initials: M
authors.lastname: De Lisio
authors.forename: Jason E
authors.initials: JE
authors.lastname: Tang
authors.forename: Gianni
authors.initials: G
authors.lastname: Parise
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Rennie
authors.forename: Steven K
authors.initials: SK
authors.lastname: Baker
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Phillips
mesh_terms: D045930:Anabolic Agents / Q000097:blood; D013006:Growth Hormone / Q000097:blood*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000502:physiology*; D055070:Resistance Training / Q000379:methods*; D015398:Signal Transduction / Q000502:physiology*; D013739:Testosterone / Q000097:blood*; D055815:Young Adult
chemical_list: D045930:Anabolic Agents; D009124:Muscle Proteins; D013739:Testosterone; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone