The boys like to watch the pelvis wiggle, but the knees don't like it very much. Upon foot contact in running/jumping, the pelvis goes too deep into the frontal plane, presenting in contralateral rotation. Ideally, the ilia should be at least level, or optimally the fee pelvis a bit higher. When the ipsilateral ilium is higher, it contributes to excessive knee abduction/internal rotation at ground contact.
This is one of the exercises I use to enhance pelvic stiffness in athletes presenting with patellofemoral stress syndrome. I do it a bit different than Frans does. BTW, Frans does not use this as a rehabilitation exercise, he uses it as a neuromuscular drill to enhance sprint mechanics. I'll have the athlete take a big step forward onto the affected leg, punch the non weight bearing ilium and hand to the ceiling, then step backwards with that same leg and return to the starting position for 3 sets of 10 reps. I begin with the athlete holding a crutch overhead, then build up to a weighted bar.


