Most muscles possess a mixture of each fiber type. The predominant fiber type in a muscle is determined by the primary function of the muscle. ATP provides the energy for muscle contraction. The three mechanisms for ATP regeneration are creatine phosphate, anaerobic glycolysis, and aerobic metabolism. Creatine phosphate provides about the first 15 seconds of ATP at the beginning of muscle contraction.
Anaerobic glycolysis produces small amounts of ATP in the absence of oxygen for a short period. Aerobic metabolism utilizes oxygen to produce much more ATP, allowing a muscle to work for longer periods.
Muscle fatigue, which has many contributing factors, occurs when muscle can no longer contract. An oxygen debt is created as a result of muscle use.
SO fibers use aerobic metabolism to produce low power contractions over long periods and are slow to fatigue. FG fibers use anaerobic metabolism to produce powerful, high-tension contractions but fatigue quickly. How will muscle cells respond to this drug? Why do muscle cells use creatine phosphate instead of glycolysis to supply ATP for the first few seconds of muscle contraction? Glycolysis cannot generate ATP as quickly as creatine phosphate.
Aerobic respiration is much more efficient than anaerobic glycolysis, yielding 36 ATP per molecule of glucose, as opposed to two ATP produced by glycolysis. Skip to content Muscle Tissue.
Learning Objectives By the end of this section, you will be able to: Describe the types of skeletal muscle fibers Explain fast and slow muscle fibers. Chapter Review ATP provides the energy for muscle contraction.
Resistance training increases the size of both type I and type II muscle fibers. Greater growth i. This results in an increased ability to generate force 2. Fast-twitch fibers can also recruit slow-twitch fibers : endurance training at high-intensity intervals can be effective in improving aerobic power 2,6. Tapering during training programs reducing volume and intensity , can also improve the strength and power of type IIA fibers without decreasing type I performance 9.
One study investigated muscle fiber changes in recreational runners training for a marathon. After 13 weeks of increasing mileage and a three week tapering cycle, not only did the functions of type I and type IIa fibers improve, but type IIa continued to improve significantly during the tapering cycle 9.
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