title: Post-exercise protein synthesis rates are only marginally higher in type I compared with type II muscle fibres following resistance-type exercise.
abstract: We examined the effect of an acute bout of resistance exercise on fractional muscle protein synthesis rates in human type I and type II muscle fibres. After a standardised breakfast (31 ± 1 kJ kg(-1) body weight, consisting of 52 Energy% (En%) carbohydrate, 34 En% protein and 14 En% fat), 9 untrained men completed a lower-limb resistance exercise bout (8 sets of 10 repetitions leg press and leg extension at 70% 1RM). A primed, continuous infusion of L: -[ring-(13)C(6)]phenylalanine was combined with muscle biopsies collected from both legs immediately after exercise and after 6 h of post-exercise recovery. Single muscle fibres were dissected from freeze-dried biopsies and stained for ATPase activity with pre-incubation at a pH of 4.3. Type I and II fibres were separated under a light microscope and analysed for protein-bound L: -[ring-(13)C(6)]phenylalanine labelling. Baseline (post-exercise) L: -[ring-(13)C(6)]phenylalanine muscle tissue labelling, expressed as (∂(13)C/(12)C), averaged -32.09 ± 0.28, -32.53 ± 0.10 and -32.02 ± 0.16 in the type I and II muscle fibres and mixed muscle, respectively (P = 0.14). During post-exercise recovery, muscle protein synthesis rates were marginally (8 ± 2%) higher in the type I than type II muscle fibres, at 0.100 ± 0.005 versus 0.094 ± 0.005%/h, respectively (P < 0.05), whereby rates of mixed muscle protein were 0.091 ± 0.005%/h. Muscle protein synthesis rates following resistance-type exercise are only marginally higher in type I compared with type II muscle fibres.
authors.affiliation: Department of Human Movement Sciences, NUTRIM School for Nutrition, Toxicology and Metabolism, Maastricht University Medical Centre, PO Box 616, 6200 MD, Maastricht, The Netherlands.
authors.forename: René
authors.initials: R
authors.lastname: Koopman
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Gleeson
authors.forename: Annemie P
authors.initials: AP
authors.lastname: Gijsen
authors.forename: Bart
authors.initials: B
authors.lastname: Groen
authors.forename: Joan M G
authors.initials: JM
authors.lastname: Senden
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Rennie
authors.forename: Luc J C
authors.initials: LJ
authors.lastname: van Loon
mesh_terms: D000328:Adult; D015444:Exercise / Q000502:physiology*; D006801:Humans; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism* / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism* / Q000502:physiology; D010649:Phenylalanine / Q000378:metabolism / Q000493:pharmacokinetics; D014176:Protein Biosynthesis / Q000502:physiology*; D020127:Recovery of Function / Q000502:physiology; D055070:Resistance Training; D013997:Time Factors; D015854:Up-Regulation / Q000502:physiology; D055815:Young Adult
chemical_list: D010649:Phenylalanine