Characteristics of the three types of muscle fibers

Describe the characteristics of the three types of muscle fibers

• Type 1 (slow twitch, oxidative, red fibers): respond to electrical stimuli slowly. Fatigue-resistant with repeated stimulation. Many mitochondria and higher lipid content. Endurance training (long-distance running) enhances metabolism of these fibers.

• Type 2a (fast twitch, oxidative-glycolytic fibers): properties intermediate between type 1 and type 2b.

• Type 2b (fast twitch, glycolytic, white fibers): respond rapidly and with greater force of contraction but fatigue rapidly. These fibers contain more glycogen and have higher myophosphorylase and myoadenylate deaminase activity. Strength training (weight-lifting, sprinters, jumpers) leads to hypertrophy of these fibers.


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