Systems biology of skeletal muscle: fiber type as an organizing principle

Abstract

Skeletal muscle force generation and contraction are fundamental to countless aspects of human life. The complexity of skeletal muscle physiology is simplified by fiber type classification where differences are observed from neuromuscular transmission to release of intracellular Ca2+ from the sarcoplasmic reticulum and the resulting recruitment and cycling of cross-bridges. This review uses fiber type classification as an organizing and simplifying principle to explore the complex interactions between the major proteins involved in muscle force generation and contraction.

Magnesium in Man: Implications for Health and Disease

“…Muscle contraction is a highly Ca 2ϩ -dependent process, initiated Ca 2ϩ release from the sarcoplasmic reticulum. Ca 2ϩ binds to troponin C and myosin to induce the conformational changes of these proteins that will result in contraction (193 (583). Both meta-analyses are limited by a relatively small patient population.…”

Functional impact of sarcopenia in respiratory muscles

“…Each motor unit type is composed of muscle fibers that are homogeneous with respect to their metabolic properties and contractile protein composition, specifically the expression of myosin heavy chain (MyHC) isoforms (Enad et al, 1989; Gransee et al, 2012; Greising et al, 2012; Sieck, 1994; Sieck et al, 1989a, 1996). In fact, this relationship forms the basis of muscle fiber type classification (Brooke and Kaiser, 1970; Edstrom and Kugelberg, 1968; Schiaffino et al, 1989; Sieck et al, 1985).…”

“…2). Based on our model of DIAm motor unit recruitment, both eupneic ventilation and ventilation stimulated by a hypoxic-hypercapnic gas mixture (10% O 2 , 5% CO 2 , balance N 2 ) require the recruitment of only type S and FR motor units, whereas higher force non-ventilatory motor behaviors require the additional recruitment of more fatigable type FInt and FF motor units (Fournier and Sieck, 1988a; Gransee et al, 2012; Greising et al, 2012; Mantilla et al, 2010; Mantilla and Sieck, 2011; Sieck, 1988, 1989, 1990, 1991, 1994, 1995; Sieck et al, 1989a, 2013; Sieck and Fournier, 1989; Sieck and Gransee, 2012). …”

Maximum Strength Estimate of Quadriceps and Brachial Biceps Muscles in Patients with Chronic Heart Disease

“…The initial loss of type I fibers, which is responsible for endurance, is followed by a consecutive increase in type II fibers. While until not long ago three types of muscle fibers were identified (I; IIa; IIb), currently fibers of the skeletal muscle are classified into four types according to their biochemical characters: (a) slow-twitch type I fatigue-resistant fibers; (b) fast-twitch type IIa fatigueresistant fibers; (c) fast-twitch type IIx fibers with intermediate fatigue-resistance; (d) and fast-twitch type IIb fatigable fibers 6 .…”