title: Resistance training alters the response of fed state mixed muscle protein synthesis in young men.
abstract: Ten healthy young men (21.0 +/- 1.5 yr, 1.79 +/- 0.1 m, 82.7 +/- 14.7 kg, means +/- SD) participated in 8 wk of intense unilateral resistance training (knee extension exercise) such that one leg was trained (T) and the other acted as an untrained (UT) control. After the 8 wk of unilateral training, infusions of L-[ring-d(5)]phenylalanine, L-[ring-(13)C(6)]phenylalanine, and d(3)-alpha-ketoisocaproic acid were used to measure mixed muscle protein synthesis in the T and UT legs by the direct incorporation method [fractional synthetic rate (FSR)]. Protein synthesis was determined at rest as well as 4 h and 28 h after an acute bout of resistance exercise performed at the same intensity relative to the gain in single repetition maximum before and after training. Training increased mean muscle fiber cross-sectional area only in the T leg (type I: 16 +/- 10%; type II: 20 +/- 19%, P < 0.05). Acute resistance exercise increased muscle protein FSR in both legs at 4 h (T: 162 +/- 76%; UT: 108 +/- 62%, P < 0.01 vs. rest) with the increase in the T leg being significantly higher than in the UT leg at this time (P < 0.01). At 28 h postexercise, FSR in the T leg had returned to resting levels; however, the rate of protein synthesis in the UT leg remained elevated above resting (70 +/- 49%, P < 0.01). We conclude that resistance training attenuates the protein synthetic response to acute resistance exercise, despite higher initial increases in FSR, by shortening the duration for which protein synthesis is elevated.
authors.affiliation: Exercise Metabolism Research Group, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Jason E
authors.initials: JE
authors.lastname: Tang
authors.forename: Jennifer G
authors.initials: JG
authors.lastname: Perco
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Moore
authors.forename: Sarah B
authors.initials: SB
authors.lastname: Wilkinson
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Phillips
mesh_terms: D000328:Adult; D000596:Amino Acids / Q000097:blood; D001706:Biopsy; D001786:Blood Glucose / Q000378:metabolism; D004435:Eating / Q000502:physiology*; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007328:Insulin / Q000097:blood; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism*; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D013997:Time Factors; D014891:Weight Lifting / Q000502:physiology*
chemical_list: D000596:Amino Acids; D001786:Blood Glucose; D007328:Insulin; D009124:Muscle Proteins