- Describe the difference between fast oxidative, slow oxidative, and fast glycolytic fibers.
- Discuss the types of activities that utilize each of these three types of fibers.
- Address this question: What does training do to muscle? In other words, what is happening in the muscle when it grows in response to working out?
Muscles differ in their functional ability due to the characteristics of the fibers they are made of. Fibers differ in many aspects that include the peak force that can be exerted, the velocity at which the muscle contracts, how fast the muscle tires and the glycolytic, oxidative and ATP capacity of the fibers.
Muscle fibers can broadly be differentiated into three groups:
Slow Oxidative: These muscle fibers twitch at a very slow rate and are very resistant to fatigue. The peak force exerted by these muscles is also very low. Slow muscle fibers have a lot of oxidative enzymes but they are low in ATP activity. Slow oxidative fibers are used for aerobic activities
Fast Oxidative Glycolytic:
Some muscle fibers can contract at a fast rate and produce a large peak force while being resistant to tiring even after many cycles. These fibers are have a large ATP activity and are high in oxidative and glycolytic enzymes. These fibers are used for anaerobic activities that need to be sustained over prolonged intervals of time.
These fibers can exert very large force and can contract at a fast rate. But this comes at the expense of the fibers tiring very easily. The muscle requires rest after a small amount of exertion to recover. These fibers have low oxidative capacity while the ATP and glycolytic activities are high. These fibers are used for anaerobic activities for short durations of time.
During aerobic training slow oxidative fibers increase in number. Anaerobic training on the other hand increases the number of fast glycolytic fibers.