the muscles of a professional sprinter are most likely to have ________. a. 80 percent fast-twitch muscle fibers and 20 percent slow-twitch muscle fibers
b. 20 percent fast-twitch muscle fibers and 80 percent slow-twitch muscle fibers
c. 50 percent fast-twitch muscle fibers and 50 percent slow-twitch muscle fibers
d. 40 percent fast-twitch muscle fibers and 60 percent slow-twitch muscle fibers