אימונים The Effects of Endurance, Strength, and Power Training on Muscle Fiber Type Shifting.

[Mike Bikov]

J Strength Cond Res. 2011 Sep 9. [Epub ahead of print]

The Effects of Endurance, Strength, and Power Training on Muscle Fiber Type Shifting.

Wilson JM, Loenneke JP, Jo E, Wilson GJ, Zourdos MC, Kim JS.

1The University of Tampa, Department of Health Sciences and Human Performance, Tampa, FL; 2Department of Health and Exercise Science, The University of Oklahoma, Norman, Oklahoma; 3Department of Nutrition, Food and Exercise Sciences The Florida State University, Tallahassee, FL; 4Department of Nutritional Sciences, University of Illinois, Champaign-Urbana, Illinois.

Muscle fibers are generally fractionated into type I, IIA, and IIX fibers. Type I fibers are specialized for 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 in order to enhance high performance activities. While interconversions between type IIA and IIX are well recognized in the literature, studies are conflicting regarding the capacity of type I and II fibers to interconvert. Therefore the purpose of this paper is to analyze the effects of various forms of exercise on type I and type II interconversions. Possible variables which may increase type II fibers and decrease type I fibers are discussed which include high velocity isokinetic contractions, ballistic movements such as bench press throws, sprints, as well as elevated levels of hormones such as triiodothyronine. Conversely a shift from type II to 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 athlete.​

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