Which statement about fast-twitch fibers is true?
A) They are more common in the leg muscles of champion sprinters than in champion marathon runners.
B) They have more mitochondria than slow-twitch fibers in the same muscle.
C) They fatigue less rapidly than slow-twitch fibers do.
D) Their abundance is more a product of training than of genetics.
E) They are more common in postural muscles than in finger muscles.

Question

Quizplus · Accepted Answer

Fast-twitch fibers are better suited for explosive power and sprinting, so they are typically more prevalent in the leg muscles of sprinters.

Answer: B 
 Fast-twitch fibers have lower oxidative capacity and generate ATP anaerobically, so they have fewer mitochondria than slow-twitch fibers.

Answer: C 
 Fast-twitch fibers fatigue more rapidly than slow-twitch fibers do because they rely on anaerobic metabolism and produce more lactic acid.

Answer: D 
 The abundance of fast-twitch fibers is determined more by genetics than by training, although training can enhance their performance.

Answer: E 
 Fast-twitch fibers are more common in muscles that produce rapid, forceful contractions, such as muscles involved in posture and eye movements, as well as in limb muscles. They are less prevalent in small muscles involved in fine motor skills, such as finger muscles.

Which Statement About Fast-Twitch Fibers Is True