In this position, the hamstrings are used for both actions: hip extension and knee flexion. This position of the leg puts the hamstrings at a very short working length, which greatly increases the chances of cramping in the muscles.

This position also makes it more likely that the other fibers of the gluteus maximus will fire to help with the hip extension, which will also externally rotate and abduct the legs. Often, a student who can keep the legs adducted and parallel when the knees are extended will find it much more challenging when the knees are flexed. In this position, all the quadriceps are lengthened, and the stretch in the rectus femoris can restrict the range of motion in knee flexion, too.