title: The effects of endurance, strength, and power training on muscle fiber type shifting.
abstract: Muscle fibers are generally fractionated into type I, IIA, and IIX fibers. Type I fibers specialize in long duration contractile activities and are found in abundance in elite endurance athletes. Conversely type IIA and IIX fibers facilitate short-duration anaerobic activities and are proportionally higher in elite strength and power athletes. A central area of interest concerns the capacity of training to increase or decrease fiber types to enhance high-performance activities. Although interconversions between type IIA and IIX are well recognized in the literature, there are conflicting studies regarding the capacity of type I and II fibers to interconvert. Therefore, the purpose of this article is to analyze the effects of various forms of exercise on type I and type II interconversions. Possible variables that may increase type II fibers and decrease type I fibers are discussed, and these include high velocity isokinetic contractions; ballistic movements such as bench press throws and sprints. Conversely, a shift from type II to type I fibers may occur under longer duration, higher volume endurance type events. Special care is taken to provide practical applications for both the scientist and the athlete.
authors.affiliation: Department of Health Sciences and Human Performance, The University of Tampa, Tampa, Florida, USA. jmwilson@ut.edu
authors.forename: Jacob M
authors.initials: JM
authors.lastname: Wilson
authors.forename: Jeremy P
authors.initials: JP
authors.lastname: Loenneke
authors.forename: Edward
authors.initials: E
authors.lastname: Jo
authors.forename: Gabriel J
authors.initials: GJ
authors.lastname: Wilson
authors.forename: Michael C
authors.initials: MC
authors.lastname: Zourdos
authors.forename: Jeong-Su
authors.initials: JS
authors.lastname: Kim
mesh_terms: D056352:Athletes; D015444:Exercise / Q000502:physiology*; D006801:Humans; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D055070:Resistance Training / Q000379:methods*