Hitting your head at 15 mph
a. has the same force of impact as being hit with a sledgehammer.
b. will rarely cause injuries.
c. has the same force of impact as being hit with a softball.

If you were running a marathon, which type of muscle fibers would be most useful to you? a. slow-twitch b. fast-twitch, type i a c. intermediate-twitch, type ii b d. slow-intermediate twitch, type i b select the best answer from the choices provided. a b c d