The Hip Flexor stretch is the single most beneficial tool for lower back tightness and pain and hip and groin pain.
What it does is stretch the illiopsas and hip flexor muscles. These muscles attach at the lower back and pelvis. So if they are tight they pull on the lower back and sacrum causing pain and more flexion, which then causes even more pain and problems.
So doing the Hip Flexor stretch at least once a day will alleviate much of the lower back pain people experience.
It is also very important to stretch out after exercise and you can also do the stretch before performing your front squats to “unlock” the hips to get down deeper.”
Senior RKC Mark Toomey also suggest adding a static hang from a pull up bar and rolling around on the floor with your hands over your head, which is also a fun thing to do anyway.
Here Andrea lays out the guidelines for executing a perfect RKC Hip Flexor Stretch. The Hip Flexor Stretches you see some people do (say, if you do a google image search) and the RKC Hip Flexor stretch differ only in the subtleties. On the outside, they look like the same move.
But knowing these subtleties will give you a more effective stretch.
Hip Flexor Stretch: WHEN to do it, HOW to do it.
Start by kneeling with one leg forward on a soft surface with your hips squared straight ahead and level.
Your legs should be hip distance apart and should both follow imaginary parallel lines.
Place your hands on your hips or the small of your back. Squeeze your glutes and push forward with your pelvis; simultaneously reaching your head to the ceiling and LENGTHENING your spine.
Keep the posterior “tuck” of the pelvis as you move forward and only go as far as you can go without losing it.
Do not allow your forward knee to travel over your toes. Exhale as you go forward and inhale as you come back up, repeat a few times moving in and out of the stretch in a gentle rhythm.
Repeat on your other leg.