Approximately 15 degrees of hip extension is required to walk normally. If hip flexors are tight then in order to walk, compensatory movement needs to take place through the lower back causing back pain and premature disc degeneration. Like other joints, if we fail to take them through their full range on a regular basis we eventually lose mobility.

Lay on your back on your mat and pull your knees to your chest. Place your hands on the inside arches of your feet and open your knees wider than shoulder-width apart. Keeping your back pressed into the mat as much as possible, press your feet into hands while pulling down on feet, creating resistance. Breathe deeply and hold for at least 30 seconds. 

Start kneeling on your mat with knees hip-width apart and hips directly over knees. Press your shins and the tops of your feet into the mat. Bring your hands to your low back, fingers pointing down, and rest palms above glutes. Inhale and lift your chest, and then slowly start to lean your torso back. From here, bring your right hand to rest on your right heel and then your left hand to your left heel. (If you can't reach your heels, turn your toes under; it will be easier to reach your heels in this modification.) Press your thighs forward so they are perpendicular to the floor. Keep your head in a relatively neutral position or, if it doesn't strain your neck, drop it back. Hold for 30 seconds. To come out of the pose, bring your hands to your hips and slowly, leading with your chest, lift your torso as you press the thighs down toward the floor.
I had compromised range of motion in my hips. I am a runner and I couldn’t increase my speed. Using this program – http://certifiedtreatment.com/hipflexors I adjusted my back and relieved the pain the tightness in my hips and lower back which allowed me to run harder and longer. Not only do I have less pain on a daily basis, but I also have more energy and stamina when I run. I find myself with better movement and sleep, and I have maximized my performance.
Low back pain (LBP) is a common disorder involving the muscles, nerves, and bones of the back.[4] Pain can vary from a dull constant ache to a sudden sharp feeling.[4] Low back pain may be classified by duration as acute (pain lasting less than 6 weeks), sub-chronic (6 to 12 weeks), or chronic (more than 12 weeks).[3] The condition may be further classified by the underlying cause as either mechanical, non-mechanical, or referred pain.[5] The symptoms of low back pain usually improve within a few weeks from the time they start, with 40–90% of people completely better by six weeks.[2]
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