How the Hip Moves while Running
by Tim Waanders, PT, DPT, FAFS
Last week, we looked at the anatomy of the hip joint and the muscles that play an important role in running. This post will be all about the biomechanics of running and what role the hip plays in it. Before we get into the hip biomechanics, it is important to briefly go over some terms of the gait cycle and what they mean. Remember, this is not meant to be an expert level course, but to provide some insight into what happens at the hip during running that every runner should have an understanding of!
The gait cycle during running can most simply be broken down into two phases: stance phase and swing phase.
STANCE PHASE → The leg on the ground from when the foot first lands until the heel lifts up and the toes come off the ground is considered to be in stance phase.
SWING PHASE → From this point, when the leg begins to swing back through to the front of your body and eventually comes back down towards the ground is considered the swing phase.
Focusing on the three planes of motion and how the body can move, we’ll start with the forward and back motion.
FLEXION → Think of it as bending towards your body. The hip is in a state of flexion anytime you’re bending at the hip, leg towards your stomach, at less than a 180* angle. The opposite of flexion is extension.
EXTENSION → You most likely already know this one but for extension, think of it as moving away from the body. The hip is in a state of extension when the leg swings backward, opening up the angle between your leg and trunk.
Now we are moving side to side with adduction & abduction.
ADDUCTION → Defined as the movement of a limb towards the midline of your body.
ABDUCTION → If you guess the movement of a limb away from the midline, then you are correct!
INTERNAL ROTATION → That would be rotation towards the center of your body.
EXTERNAL ROTATION → And rotation away from the center of your body.
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Having reviewed some of the more technical terms for the gait cycle, let’s jump into the biomechanics of the hip when running.
THE HIP IN STANCE PHASE
Starting at the beginning of stance phase, the hip is in a state of flexion, adduction, and internal rotation (IR). At this point, the glutes and hamstrings are activated and are working to control the motion of the hip and the rest of the lower extremity to prevent excessive flexion, adduction, and IR. As the rest of your body continues to move forward over the stance leg, the glutes and hamstrings generate power and extend the hip joint to pull your leg behind you as you push off the foot on the ground, ending stance phase & entering swing phase. Abduction and external rotation (ER) also occur at this point, as the hip takes the energy it loaded up from the beginning of the phase and uses it for propulsion through the rest of the cycle.
Common compensations that indicate a lack of true hip extension include excessive low back extension and overstriding. If the hip cannot extend properly, due to possible tightness in the hip flexors or another anterior (front) hip structure, then the lumbar spine will have to excessively extend in order to allow the leg to get far enough back for propulsion forward. This of course can lead to significant low back pain over time. Overstriding occurs when the foot lands at the beginning of stance phase but is too far in front of the body. This can lead to a multitude of issues, but if the body ends up compensating for lack of hip extension by overstriding, it is doing so because the stride length is not long enough to generate enough power to properly propel the body forward.
Looking at the pelvis specifically, it anteriorly tilts (tilts forward) throughout the entirety of stance phase. This is necessary in order to have adequate stride length, allowing for the maximal hip extension required. If the pelvis anteriorly tilts too excessively, however, it can lead to overlengthened hamstrings, placing them at risk for strains, tears, or tendinopathy.
THE HIP IN SWING PHASE
At the start of swing phase, the hip flexors work to drive the thigh forward. This momentum is what helps continue to propel the body forward after the end of the push-off during stance phase. After a point where the hip reaches peak flexion (can be as much as 65 degrees of flexion, depending on speed), the hamstrings and glutes kick back in to extend the hip and prepare for the initial contact of the foot hitting the ground – initiating stance phase. This should emphasize the importance of having strong and powerful hip extensors like the glutes and hamstrings!
Another common compensation is the hip drop (aka a Trendelenburg gait). While this impacts both phases, the drop occurs in the swing leg. The glutes work to provide stability at the pelvis and prevent excessive tilting from side-to-side. If the glutes are too weak in the stance leg, the hip drops in the swing leg and the stance leg can be involved in excessive internal rotation or adduction of the thigh, causing problems down the chain.
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Look out next week for our post on what you can do to improve the mobility, strength, and stability of your hips and prevent injury in the future! Remember, if you are feeling any pain or weakness in any part of your body at this point in time, it is best to reach out to a physical therapist to get an assessment and formulate a personal plan to prevent things from getting worse and get you back to feeling 100%! Give our office a call if you want to get something scheduled!