Muscles that are constantly active, such as those maintaining our body posture, have a high proportion of
A) fast, fatigue-resistant fibers.
B) fast, fatigue-susceptible fibers.
C) slow, fatigue-resistant fibers.
D) slow, fatigue-susceptible fibers.

Question

Quizplus · Accepted Answer

Muscles that are constantly active, such as those involved in maintaining body posture, require fibers that can sustain contractions for long periods without fatiguing. This means they need slow-twitch (Type I) fibers that are fatigue-resistant. Fast-twitch (Type II) fibers are better suited for activities that require quick and powerful contractions, such as sprinting or weight lifting, but they tire quickly. So option A and B can be eliminated. Slow-twitch fibers are not susceptible to fatigue, so option D can also be eliminated, leaving option C as the best choice.

Muscles That Are Constantly Active, Such as Those Maintaining Our