title: Resistance exercise load does not determine training-mediated hypertrophic gains in young men.
abstract: We have reported that the acute postexercise increases in muscle protein synthesis rates, with differing nutritional support, are predictive of longer-term training-induced muscle hypertrophy. Here, we aimed to test whether the same was true with acute exercise-mediated changes in muscle protein synthesis. Eighteen men (21 ± 1 yr, 22.6 ± 2.1 kg/m(2); means ± SE) had their legs randomly assigned to two of three training conditions that differed in contraction intensity [% of maximal strength (1 repetition maximum)] or contraction volume (1 or 3 sets of repetitions): 30%-3, 80%-1, and 80%-3. Subjects trained each leg with their assigned regime for a period of 10 wk, 3 times/wk. We made pre- and posttraining measures of strength, muscle volume by magnetic resonance (MR) scans, as well as pre- and posttraining biopsies of the vastus lateralis, and a single postexercise (1 h) biopsy following the first bout of exercise, to measure signaling proteins. Training-induced increases in MR-measured muscle volume were significant (P < 0.01), with no difference between groups: 30%-3 = 6.8 ± 1.8%, 80%-1 = 3.2 ± 0.8%, and 80%-3= 7.2 ± 1.9%, P = 0.18. Isotonic maximal strength gains were not different between 80%-1 and 80%-3, but were greater than 30%-3 (P = 0.04), whereas training-induced isometric strength gains were significant but not different between conditions (P = 0.92). Biopsies taken 1 h following the initial resistance exercise bout showed increased phosphorylation (P < 0.05) of p70S6K only in the 80%-1 and 80%-3 conditions. There was no correlation between phosphorylation of any signaling protein and hypertrophy. In accordance with our previous acute measurements of muscle protein synthetic rates a lower load lifted to failure resulted in similar hypertrophy as a heavy load lifted to failure.
authors.affiliation: Exercise Metabolism Research Group, Department of Kinesiology, McMaster Univ., 1280 Main St., West, Hamilton, Ontario, L8S4L8, Canada.
authors.forename: Cameron J
authors.initials: CJ
authors.lastname: Mitchell
authors.forename: Tyler A
authors.initials: TA
authors.lastname: Churchward-Venne
authors.forename: Daniel W D
authors.initials: DW
authors.lastname: West
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Burd
authors.forename: Leigh
authors.initials: L
authors.lastname: Breen
authors.forename: Steven K
authors.initials: SK
authors.lastname: Baker
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Phillips
mesh_terms: D001706:Biopsy; D006801:Humans; D006984:Hypertrophy; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009124:Muscle Proteins / Q000378:metabolism; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology*; D010766:Phosphorylation; D055070:Resistance Training / Q000379:methods*; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D014891:Weight Lifting / Q000502:physiology; D055815:Young Adult
chemical_list: D009124:Muscle Proteins; D038762:Ribosomal Protein S6 Kinases, 70-kDa