I recently had a client come in for treatment for low back pain. Sheila normally does a mixed workout and runs a bit. Recently she had decided to walk to work every day and time herself, moving as fast as she could. She had low back pain. On examination I discovered her hip flexors, and notably her psoas, was tight. Releasing the muscle dissipated the pain. She has gone back to running and has no pain.
This muscle group connects the lower back and pelvis to the legs at the upper part of the inside thigh. These muscles lift the leg up and if you rotate your leg outwards and back it's the powerful muscle the pulls it in. The hip flexors take part in walking, running and kicking and any movement that drives the leg forward. It is an important postural muscle that helps keep you upright.
The psoas is part of this system. It is a long ropey muscle that extends from the lower vertebrae in the small of your back through the middle of the pelvis and on to the top of the inner thigh. If it is too tight you may feel tight hamstrings as your pelvis is pulled into a forward rotation. Tight hip flexors not only stress the hamstrings they pull on the vertebrae of the lower back to which they are attached. This causes pain and tightness and often results in vertebrae being displaced, and can contribute to disc prolapse.
But it's not just athletes, all sorts of people have issues. I have noticed that people who pride themselves on being able to walk briskly have issues with this muscle. So are they all doing something wrong?
I have a theory. I think overstriding is to blame. Left to walk barefoot no-one takes a long stride. It necessitates a strong heelstrike which hurts. It involves a heavy impact which is uncomfortable. Think about how you walk on the hard surface around a swimming pool. Imagine you were walking on a concrete driveway in your bare feet and you had to suddenly sprint to stop a child from going on to the road.
How would you move? You'd take lots of little fast strides up on the balls of your feet. If this is our natural evolved movement then the long stride is only facilitated by the cushioning of a shoe. Most of us have adapted to this but at what cost? The shortened hip flexors!
Taking a muscle from hyperextension into deep contraction quickly causes stress, that's why footballers often have issues with this muscle. They use this muscle for that explosive kick.
Our natural gait is to walk when we need to move slowly, move into a run if more pace is required and then if we need to go fast, to sprint. If we do this while keeping the bodyweight and pelvis above the feet, the hip flexor's job becomes less stressful, reducing the likelihood of injury. This is how we learned to walk. We change as we become accustomed to footwear. To regain that pattern is certainly difficult and minimalist footwear can help with that change.