title: Resistance training reduces the acute exercise-induced increase in muscle protein turnover.
abstract: We examined the effect of resistance training on the response of mixed muscle protein fractional synthesis (FSR) and breakdown rates (FBR) by use of primed constant infusions of [2H5]phenylalanine and [15N]phenylalanine, respectively, to an isolated bout of pleiometric resistance exercise. Trained subjects, who were performing regular resistance exercise (trained, T; n = 6), were compared with sedentary, untrained controls (untrained, UT; n = 6). The exercise test consisted of 10 sets (8 repetitions per set) of single-leg knee flexion (i.e., pleiometric muscle contraction during lowering) at 120% of the subjects' predetermined single-leg 1 repetition maximum. Subjects exercised one leg while their contralateral leg acted as a nonexercised (resting) control. Exercise resulted in an increase, above resting, in mixed muscle FSR in both groups (UT: rest, 0.036 +/- 0.002; exercise, 0.0802 +/- 0.01; T: rest, 0.045 +/- 0.004; exercise, 0.067 +/- 0.01; all values in %/h; P < 0.01). In addition, exercise resulted in an increase in mixed muscle FBR of 37 +/- 5% (rest, 0.076 +/- 0.005; exercise, 0.105 +/- 0.01; all values in %/h; P < 0.01) in the UT group but did not significantly affect FBR in the T group. The resulting muscle net balance (FSR - FBR) was negative throughout the protocol (P < 0.05) but was increased in the exercised leg in both groups (P < 0.05). We conclude that pleiometric muscle contractions induce an increase in mixed muscle protein synthetic rate within 4 h of completion of an exercise bout but that resistance training attenuates this increase. A single bout of pleiometric muscle contractions also increased the FBR of mixed muscle protein in UT but not in T subjects.
authors.affiliation: Metabolism Unit, Shriners Burns Institute, and Departments of Surgery and Anesthesiology, University of Texas Medical Branch, Galveston, Texas 77550-2725, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Phillips
authors.forename: K D
authors.initials: KD
authors.lastname: Tipton
authors.forename: A A
authors.initials: AA
authors.lastname: Ferrando
authors.forename: R R
authors.initials: RR
authors.lastname: Wolfe
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology; D009994:Osmolar Concentration; D010649:Phenylalanine / Q000097:blood / Q000378:metabolism; D010806:Physical Education and Training; D012016:Reference Values; D013997:Time Factors; D014891:Weight Lifting / Q000502:physiology
chemical_list: D009124:Muscle Proteins; D010649:Phenylalanine