When entering into discussions about the health consequences of sitting, people are often told that over time if we sit for too long our hip muscles actually shorten in length making it harder for us to stand upright. While there are some changes that occur to the hip muscles, it is interesting to look at the changes to the hip muscles when moving from a sitting to a standing position.
The Hamstrings
Lets take the hamstring muscles. These are the big muscles that sit at the back of the thighs and connect the bottom of your pelvis to the bottom of your knee joint. The hamstring muscles are responsible for both bending the knee and extending or straightening the hip. In both of these movements the muscle contracts and shortens in length. When we are in a seated position, both the knees and the hips are in a flexed or bent position. When we stand up we extend both of these joints. Hence looking at the position of the hamstrings in both positions, we find that they remain the same length whether we sit or stand.
The Quadriceps
On the front side of the thigh are the quadriceps. The quadriceps connect the front part of the pelvis to the patella tendon which attaches at the top of the shin. The quadriceps are one of the hip flexor muscles that are responsible for flexing or bending the hips, as well as extending the knee. As with the hamstrings, the quadricep muscles remain the same length when we move from a sitting to a standing position.
The Iliopsoas
There is however one more important muscle in the hip region that does change length when we change from a sitting to a standing position. This muscle is the iliopsoas muscle with is another important hip flexor muscle. This muscle connects from the upper thigh bone to the lower back and even has tissue connections with the diaphragm which is the muscle responsible for breathing. When we are in a seated position this muscle is in a relatively shortened position. As we stand, the muscle extends and stretches. The iliopsoas muscle is the main muscle that is affected from prolonged sitting.
How can we offset the effects?
To offset the effects of too much sitting, we are often told to stretch out our hip flexors and there are a couple of ways to do this. One of the common ways people are told to stretch these muscles is to stand and bend the knee to try and bring the heel towards their buttock. This predominantly stretches the quadriceps muscles. To target the iliopsoas muscle we need to perform a stretch that tilts our pelvis down to extend the hips. This can be achieved by gently lunging forward and squeezing the buttock muscle.