Exercise Physiology: Theory and Application to Fitness and Performance 9th Edition by Scott Powers, Edward Howley

Exercise 8

Discuss the relationship between force and speed of movement during a muscular contraction.

Step 1 of 2

Muscles respond to stimulus with a simple twitch. After a stimulus, there is a brief latent period before the muscle shortens. It is followed by contraction which lasts for about 4 milliseconds. The muscle then relaxes and returns to its original state. The relaxation phase lasts for about50 milliseconds before another cycle starts.

The speed and timing of the contraction varies with the individual muscle fiber types that make up the muscle. While fast fibers contract quickly in response to a stimulus, slow fibers show slow response. This is due to the fact that the sarcoplasmic reticulum of the fast fibers releases calcium ions at a faster pace. Moreover, fast fibers possess higher ATPase (adenosine triphosphatase) activity compared to the slow fibers.