The current results indicate that (1) hypertrophy of the quadriceps femoris is associated with a proportional increase in pennation angle but not necessarily in fascicle length, and (2) training-induced changes in muscle size and pennation do not evenly occur among the quadriceps, along or across a muscle.

The sprinters in this study presented greater muscularity of the thigh and psoas major but not the monoarticular knee extensor or flexor muscles. The rectus femoris, in particular, may play an important role during the swing phase of sprinting.