Chapter 32, Problem 38A

Summary Introduction

To write:

Importance of having muscles with both slow-twitch as well as fast-twitch fibers.

Introduction:

Skeletal muscles consist of two forms of fibers: slow-twitch (type I) and fast-twitch (type II).

Both types of fibers are very essential for the normal functioning of the muscles.

Explanation of Solution

Muscles with predominantly slow-twitch fibers help in long-endurance events such as distance running. Muscles with predominantly fast-twitch fibers fatigue much faster but are used for powerful yet short-lived events such as sprinting.

Neither slow-twitch nor fast-twitch fibers alone in skeletal muscles can be beneficial for the individual. On one hand, slow twitch muscles provide continuous energy and offer extended muscle contraction. It has high endurance ability.

Fast-twitch muscles use anaerobic metabolism for fuel. They fire rapidly but fatigue easily.

For marathoners, slow-twitch muscles are beneficial while for sprinters, fast-twitch muscles are essential. However, neither one alone is completely sufficient for the individual.

Conclusion

For any individual, both fast-twitch as well as slow-twitch muscles are essential because one might be beneficial for long runs while the other may be beneficial for immediate responses.