Question

a mother sprints across the yard to grab her small child before he enters the street. the mother is using her __________. a. type i a slow - twitch muscle fibers that provided her with a fast burst of movement b. type ii b fast - twitch muscle fibers that respond quickly and provide her with speed and strength c. type i b intermediate - twitch muscle fibers that respond quickly because they are delivered energy aerobically d. type ii a fast - twitch muscle fibers that act rapidly because they are delivered energy anaerobically

Explanation:

• Type I (slow - twitch) fibers are for endurance activities, not fast bursts. So option A is incorrect.
• There is no type IB fiber classification in the standard muscle fiber types. So option C is incorrect.
• Type IIA fibers can use both aerobic and anaerobic metabolism, but type IIB fibers are pure fast - twitch, responding quickly for speed and strength which is needed for a sprint (a fast, high - intensity movement).

Answer:

B. type II B fast - twitch muscle fibers that respond quickly and provide her with speed and strength