Functional properties of human muscle fibers after short-term resistance exercise training.
The aim of this study was to assess the relationships between human muscle fiber hypertrophy, protein isoform content, and maximal Ca(2+)-activated contractile function following a short-term period of resistance exercise training. Six male subjects (age 27 +/- 2 yr) participated in a 12-wk progressive resistance exercise training program that increased voluntary lower limb extension strength by >60%. Single chemically skinned fibers were prepared from pre- and posttraining vastus lateralis muscle biopsies. Training increased the cross-sectional area (CSA) and peak Ca(2+)-activated force (P(o)) of fibers containing type I, IIa, or IIa/IIx myosin heavy chain by 30-40% without affecting fiber-specific force (P(o)/CSA) or unloaded shortening velocity (V(o)). Absolute fiber peak power rose as a result of the increase in P(o), whereas power normalized to fiber volume was unchanged. At the level of the cross bridge, the effects of short-term resistance training were quantitative (fiber hypertrophy and proportional increases in fiber P(o) and absolute power) rather than qualitative (no change in P(o)/CSA, V(o), or power/fiber volume).
Widrick
Jeffrey J
JJ
Department of Exercise and Sport Science, Oregon State University, Corvallis, Oregon 97331, USA. jeff.widrick@orst.edu
Stelzer
Julian E
JE
Shoepe
Todd C
TC
Garner
Dena P
DP
D000222:Adaptation, Physiological; D000328:Adult; D001696:Biomechanical Phenomena; D001706:Biopsy; D001823:Body Composition / Q000502:physiology; D002118:Calcium / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry / Q000502:physiology*; D018657:Muscle Fibers, Slow-Twitch / Q000737:chemistry / Q000502:physiology*; D018482:Muscle, Skeletal / Q000737:chemistry / Q000502:physiology*; D009218:Myosins / Q000032:analysis; D020033:Protein Isoforms / Q000032:analysis; D013314:Stress, Mechanical
D020033:Protein Isoforms; D009218:Myosins; D002118:Calcium