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Animal Muscles

Contain myoglobin oxygen binding protein contain many

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Unformatted text preview: Slow-twitch muscle fibers Fast-twitch muscle fibers •  “Oxidative” or “red” muscle. •  Contain myoglobin: oxygen binding protein. •  Contain many mitochondria. ! •  Are well-supplied with blood vessels. •  Maximum tension develops slowly, but is highly resistant to fatigue. ! What Determines Muscle Strength and Endurance? ! Slow-twitch fibers have reserves of glycogen and fat; can produce ATP as long as oxygen is available. Muscles with high proportion of slow-twitch fibers are good for aerobic work (e.g., long distance running, cycling, swimming, etc.) ! What Determines Muscle Strength and Endurance? ! Fast-twitch fibers: •  “Glycolytic” or “white” muscle. •  Fewer mitochondria, fewer blood vessels, little or no myoglobin. •  Develop greater maximum tension faster, but fatigue more quickly. •  Can’t replenish ATP for prolonged contraction. ! Type I (slow; dark fibers) and Type II (fast; light fibers) human skeletal muscle. LM. Slow-and Fast-Twitch Muscle Fibers (Part 1) Distance cyclist Sprinter ! ! Slow-twitch Fast-twitch ! ! What Determines Muscle Strength and Endurance? The proportion of fast- and slow-twitch fibers in skeletal muscles is determined mostly by genetic heritage. Training can alter muscle properties to a certain extent. ! What Determines Muscle Strength and Endurance? Exercise: • Anaerobic activities increase muscle strength: new actin and myosin filaments form, muscle gets larger. • Aerobic activities increase endurance: oxidative capacity is enhanced by increasing number of mitochondria, blood vessels, myoglobin, and enzymes. !...
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