When a client squats and maintains a slight anterior pelvic tilt, the hamstring is actually lengthening during the descent. Clients with tight lateral hamstrings will reach the end of their hamstring range of motion before they reach full squat depth. As the descent continues and the client attempts to get the femur parallel to the floor the short lateral hamstring will begin to force the pelvis to rotate posteriorly.
Clients who “tuck under” should not be loaded until they have developed enough flexibility to prevent the posterior rotation. Loading a spine that is moving into flexion is a prescription for disaster. The spine is meant to be loaded in a slightly lordotic position (anterior tilt). Loading in a posterior tilt can be dangerous.
Improve this condition by having the client foam roll the hamstring, stretch the hamstring, perform glut activation & then do the squats.