As athletes you hear over and over from coaches to tighten up the core and flex those butt cheeks. Belly Button to Spine. But Why? Why do we practice mid-line stabilization again and again, with ALL movements? This is a great video that shows an example of an athlete doing all the right things..almost. He actively stretches, PNF's, uses the lacrosse ball, but those hammies still won't let up. Proper movement mechanics stem from core to extremities.