Muscle: The Gripping Story of Strength and Movement

Meals (Bones), a professor of orthopedic surgery at UCLA, delivers a thorough overview of muscles and how they operate. Expounding on their biology, Meals explains that, on a molecular level, muscle consists of two protein filaments, actin and myosin, that work in tandem to convert “chemical energy into physical force.” He surveys different kinds of muscles, noting that skeletal muscles (those attached to bones) make up 40% of human body mass, smooth muscles in the trachea and intestines are responsible for moving air and solids through the body, and cardiac muscle in the heart contracts to keep blood circulating. He writes that while skeletal muscle is mostly under voluntary control, smooth muscle operates outside of consciousness and serves a crucial role in the autonomic nervous system, which is responsible for activating the fight-or-flight response (dilating pupils and lung airways to see farther and “capture more oxygen” when threatened), as well as promoting digestion and lowering one’s heart rate when resting. The scientific insights illuminate the abilities and oddities of the human body (goosebumps are caused by the contraction of small muscles connecting hair follicles to the skin), and the fitness advice is a boon (aerobic exercise for at least 150 minutes per week “improves the heart’s muscle tone”). The result is a strong primer on an essential part of the human body. Illus. (June)