|Rivas, Donato Americo -|
|Fielding, Roger A. -|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: May 19, 2011
Publication Date: March 8, 2013
Citation: Rivas, D., Fielding, R. 2013. Skeletal muscle. In: Caballero, B., editor. Encyclopedia of Human Nutrition - 3rd Edition. Amsterdam: Adcademic Press. p. 193-199. Technical Abstract: There are approximately 650-850 muscles in the human body these include skeletal (striated), smooth and cardiac muscle. The approximation is based on what some anatomists consider separate muscle or muscle systems. Muscles are classified based on their anatomy (striated vs. smooth) and if they are voluntarily or involuntarily controlled. The simple distinction is between muscle cells attached to the skeleton and those in the walls of hollow organs. Functions of muscle include movement, stability and posture, heat production, circulation, and digestion. As a result of the diverse and abundant research that has been or is currently being conducted on muscle tissue we believe that in this brief review we could not cover all important aspects of the different types of muscle. To this end, this chapter will primarily focus on recent research pertaining to skeletal muscle adaptation to nutrition, exercise, aging and chronic disease. This will be accomplished by 1) introducing skeletal muscle’s structure and function, 2) summarizing its adaptive responses to nutrition and contractile activity and 3) changes with aging and chronic disease. Skeletal muscle is highly malleable tissue that is a central factor in whole-body health and is essential for maintaining energy homeostasis. Skeletal muscle accounts for approximately 45-50% of body mass in non-obese individuals and plays a fundamental role in locomotion, O2 consumption, whole-body energy metabolism, and substrate turnover & storage (Zierath & Hawley, 2004). Skeletal muscle is responsible for approximately 20%–30% of resting oxygen consumption (stump cs et al annals med 2006). Unlike the metabolic rate in tissues like, brain and kidney which are constantly sustained and fluctuate little throughout the course of one day, skeletal muscle metabolism changes considerably from resting to maximal physical activity, during which muscle O2 consumption can account for up to 90% of the whole body oxygen uptake. Furthermore, in healthy individuals skeletal muscle accounts for approximately 80% of whole body insulin-stimulated glucose uptake but in normal-weight subjects with insulin resistance, total body glucose metabolism is reduced by up to 40% (DeFronzo et al, 1985). These data highlight the importance of that any change in skeletal muscle mass, metabolic rate, and/or response to hormones and other circulating factors would significantly affect the body’s overall energy stores and metabolism.