You’re probably thinking, “What does limited quadriceps flexibility have to do with increasing my risk for a hamstring strain?” Well, you’re not alone, as I was initially a little stumped by this as well. But after consulting with some of the top physical therapy minds at USC this past week, it’s all been made crystal clear.
Imagine the late terminal swing phase of running, when one leg is out in front of you (hip flexed and knee extended) and the other leg has just pushed off from the ground behind you. The limited quadriceps flexibility that can potentially put you at greater risk for a hamstring strain is on the CONTRALATERAL (opposite) side of the hamstrings during late terminal swing. The leg that has just propelled you off the ground during running is in knee flexion and hip extension - both positions that maximally lengthen the quadriceps. If the quadriceps (ie rectus femoris) has limited flexibility, it can pull the pelvis into ANTERIOR PELVIC TILT. This contralateral anterior pelvis tilt can translate to the ipsilateral pelvis, placing it into anterior pelvic tilt as well. This can place excessive stretch/lengthening on the hamstrings of the ipsilateral side, as they originate at the ischial tuberosity. This excessive lengthening, without adequate eccentric control or adequate hamstring flexibility can be a recipe for disaster and lead to a hamstring strain.