How to: Lie on your back with your right knee bent and foot flat on the floor (a). Extend your left leg up to the ceiling and wrap a strap around the sole of your left foot (b). While holding both ends with your left hand, extend your right arm directly out to the side in order to anchor yourself (c). Slowly let the left leg fall toward the left while keeping your right side grounded. Hold for six to eight breaths, then repeat on the opposite side.
Place a mini band around your ankles and spread your feet about shoulder-width apart. Keeping your legs relatively straight (you want the motion to come from your hips) and toes pointing forward, walk forward 10 steps, then backward 10 steps. Take a short break and then walk to the right 10 steps, then to the left 10 steps. Again, focus on keeping your legs straight and toes pointing forward.

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.

People routinely have no pain despite the presence of obvious arthritic degeneration, herniated discs, and other seemingly serious structural problems like stenosis and spondylolistheses. This surprising contradiction has been made clear by a wide variety of research over the years, but the most notable in recent history is Brinjikji 2015. There are painful spinal problems, of course — which was also shown by Brinjikji et al in a companion paper — but they are mostly more rare and unpredictable than most people suspect, and there are many fascinating examples of people who “should” be in pain but are not, and vice versa. Spinal problems are only one of many ingredients in back pain. BACK TO TEXT
The side of the pain on its own doesn’t tell us much, and most of the one-sided sources of pain are viscera that usually cause abdominal pain instead of back pain, or in addition to it. In other words, the only reason to worry about right or left lower back pain is if it is otherwise worrisome: if you have other red flags or significant non-back symptoms.

You're more likely to get a hip flexor injury if you've had one in the past, you don't warm up properly before engaging in athletic activity, your muscles are already tight or stiff, or your muscles are weak from being overused. If, while exercising, you try to do too much at once in too short an amount of time, you can also put yourself at risk for a hip flexor injury.