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About Contractions, muscle disorders, and the effects of exercise Types of contractions Isometric contractions- muscle does not shorten & no movement occurs. Ex.- pushing against a wall Isotonic contractions - produces movement at a joint such as walking, running or breathing Twitch contractions- quick jerky contraction Tetanic contractions – contractions which do not relax Atrophy Atrophy is when muscles shrink in mass from lack of use. Why do you think this occurs? It’s not a bad thing… Muscular hypertrophyincrease in muscle size MUSCULAR DISORDERS Myo – prefix that means “muscle” Myalgia – muscle pain Myopathies – muscle disorders MUSCULAR DISORDERS Injury • Strain – tearing or stretching fibers, caused by overexertion or trauma • A strain near a joint can be a SPRAIN • Inflammation – myositis • Crush injuries can release muscle contents and cause kidney failure • Stress can cause neck and back pain MUSCULAR DISORDERS Infections • Poliomyelitis was an infection of muscles that caused paralysis and often death. • The president Franklin Delano Roosevelt had polio and spent most of his adult life in a wheelchair. • “Polio” was common in the early 20th century has nearly been eliminated by a comprehensive vaccination program. MUSCULAR DISORDERS Muscular Dystrophy • A genetic disease • Is actually a group of disorders characterized by muscle atrophy • Is often fatal MUSCULAR DISORDERS Multiple Sclerosis • An autoimmune disease characterized by chronic fatigue and weakness Effects of exercise Muscular hypertrophyincrease in muscle size Improved tone and posture More efficient heart and lung function Decreased fatigue Strength training Increases the number of microfilaments in each fiber Increases muscle mass Endurance training Increases the muscles’ ability to sustain moderate exercise over a long period Also called “cardio” or “aerobic” exercise Does not usually result in hypertrophy More blood vessels develop to meet the need of the muscles. This increases efficiency of delivery of oxygen and nutrients to muscles.
