You are passively stretching the hip flexors of a patient in the position of prone hip extension and knee flexion

You later note that the patient demonstrates greater hip extension passive range of motion (PROM) when you allow the knee to be straight during the stretching procedure. The reason for the improved hip extension PROM may best be explained by ____________________.
a. elimination of active insufficiency that occurred during the original position
b. elimination of passive insufficiency that occurred during the original position
c. elimination of both active and passive insufficiency that occurred during the original position
d. activation of passive insufficiency that occurred in the second position

ANS: B
Because the activity being performed was purely passive, active insufficiency cannot be possible.
Active insufficiency would require a production of cross-bridges. In the initial position, the rectus
femoris would have been elongated over both joints over which it acts, and this could have led to
the muscle being in a passively insufficient position. When the therapists allowed the knee to be
straight, the muscle was no longer elongated over one of its joints (the knee) and therefore could
be elongated more over the other joint (hip).