Anatomy Corner: Hip Extension and Hip Flexion!
Last time, I talked about the Psoas, a mysteriously named muscle with many functions including flexing one's hips. Exactly what does that mean?
The word flexion actually means to decrease the angle between two bones at joint. Flexing your biceps involves flexing your elbow joint, bringing the hand closer to the shoulder. Thus hip flexion would be bringing the foot closer to the midline.
Now the catch with hip flexion is that most of us sit in chairs and end up in a position of hip flexion and knee flexion (bent knees) and retain that position for many hours a day. We know now that our bodies process the movement or lack thereof and take the shape that we most frequently inhabit, for better or worse. If you primarily flex the hips and never extend them, you may have chronically shortened hamstrings, limited range of flexion and limited range of extension, for starters!
Extension (as a definition) increases the angle between the bones in a joint. When you extend your knee, you are straightening your knee. When you are extending your hip, your leg is essentially moving backwards in space, say 10-20 degrees. When you walk, run, or lunge, you have one hip passing through extension. Now why the fuss about these two words?
Well, most of us work the hip flexors (including the psoas and iliacus) most of the time- sitting, practicing while seated, cycling, driving...but only in a limited range, i.e. knees and hips bent to 90 degrees. We need to balance out the movements of the hips a bit more- add more extension and more varieties of flexion. For example, sitting cross legged, sitting on the floor, squatting, kneeling, etc. all require more varieties of hip flexion. To get more hip extension in your life, you can add some restorative exercises like standing apanasana, lunges (lots of lunges!) and go walk (not on a treadmill). That way, you don't lose your capacity to move those joints to their full capacity, and you will have loaded the tissues in more diverse ways.