Question

Type II muscle fibers (fast-twitch) are helpful in what? Where would it be located? Type of athlete?

a) Helpful in explosive, powerful movements, located in muscles for sprinting, found in sprinters
b) Helpful in long-endurance activities, located in the core muscles, found in swimmers
c) Helpful in slow, sustained movements, located in the hand muscles, found in pianists
d) Helpful in balance and coordination, located in the calf muscles, found in dancers

Answer 1

Type II muscle fibers are specialized for short, powerful movements and are found in higher concentrations in athletes like sprinters. They include Type IIa, which are aerobic, and Type IIx, which are the fastest and support only brief high-intensity contractions.

Step-by-step explanation:

Type II muscle fibers, also known as fast-twitch fibers, are specialized for short, explosive, powerful movements. They are found in higher concentrations in muscles used for quick, intense activities, such as more in the muscles used for sprinting. Therefore, they are typically found in abundance in athletes who specialize in these types of activities, like sprinters. Type II fibers are less dense in mitochondria and myoglobin compared to Type I (slow-twitch) fibers and can contract more quickly and with greater force. However, they fatigue quickly and rely on anaerobic metabolism, leading to a quicker onset of muscle fatigue during prolonged activity.

Specifically, Type IIx or Type IIb fibers, known as white muscle due to the lower presence of mitochondria and myoglobin, are the fastest and can support only brief periods of high-intensity contraction. On the other hand, Type IIa fibers are more similar to slow-twitch fibers in that they are still aerobic and rich in mitochondria and capillaries, being capable of a bit more endurance than Type IIx but are still geared towards quick, powerful movements rather than sustained endurance.