title: Effect of resistance training on single muscle fiber contractile function in older men.
abstract: The purpose of this study was to examine single cell contractile mechanics of skeletal muscle before and after 12 wk of progressive resistance training (PRT) in older men (n = 7; age = 74 +/- 2 yr and weight = 75 +/- 5 kg). Knee extensor PRT was performed 3 days/wk at 80% of one-repetition maximum. Muscle biopsy samples were obtained from the vastus lateralis before and after PRT (pre- and post-PRT, respectively). For analysis, chemically skinned single muscle fibers were studied at 15 degrees C for peak tension [the maximal isometric force (P(o))], unloaded shortening velocity (V(o)), and force-velocity parameters. In this study, a total of 199 (89 pre- and 110 post-PRT) myosin heavy chain (MHC) I and 99 (55 pre- and 44 post-PRT) MHC IIa fibers were reported. Because of the minimal number of hybrid fibers identified post-PRT, direct comparisons were limited to MHC I and IIa fibers. Muscle fiber diameter increased 20% (83 +/- 1 to 100 +/- 1 microm) and 13% (86 +/- 1 to 97 +/- 2 microm) in MHC I and IIa fibers, respectively (P < 0.05). P(o) was higher (P < 0.05) in MHC I (0.58 +/- 0.02 to 0.90 +/- 0.02 mN) and IIa (0.68 +/- 0.02 to 0.85 +/- 0.03 mN) fibers. Muscle fiber V(o) was elevated 75% (MHC I) and 45% (MHC IIa) after PRT (P < 0.05). MHC I and IIa fiber power increased (P < 0.05) from 7.7 +/- 0.5 to 17.6 +/- 0.9 microN. fiber lengths. s(-1) and from 25.5 to 41.1 microN. fiber lengths. s(-1), respectively. These data indicate that PRT in elderly men increases muscle cell size, strength, contractile velocity, and power in both slow- and fast-twitch muscle fibers. However, it appears that these changes are more pronounced in the MHC I muscle fibers.
authors.affiliation: Human Performance Laboratory, Ball State University, Muncie, Indiana 47306, USA. strappe@bsu.edu
authors.forename: S
authors.initials: S
authors.lastname: Trappe
authors.forename: D
authors.initials: D
authors.lastname: Williamson
authors.forename: M
authors.initials: M
authors.lastname: Godard
authors.forename: D
authors.initials: D
authors.lastname: Porter
authors.forename: G
authors.initials: G
authors.lastname: Rowden
authors.forename: D
authors.initials: D
authors.lastname: Costill
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007551:Isotonic Contraction / Q000502:physiology*; D007719:Knee Joint / Q000502:physiology; D008297:Male; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000737:chemistry / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000032:analysis / Q000502:physiology; D018994:Myosin Light Chains / Q000032:analysis / Q000502:physiology
chemical_list: D018994:Myosin Light Chains; D018995:Myosin Heavy Chains