Even though it seems like your legs are moving forward and backward when you’re running, in reality, the femur (your thigh bone) both rotates and tilts in the hip socket, Kalika explains. It’s the hip adductors—most notably the gluteus medius—that keeps the femur sitting in the socket as designed. (The hip adductors are the muscles that move your legs inward.) Any weaknesses make the joint unstable, and can contribute to poor running mechanics, hip drop (when the pelvis drops to one side), too-narrow stances, and aggravated tissues throughout the entire body, Sauer says.

Meanwhile, many non-dangerous problems can cause amazingly severe back pain. A muscle cramp is a good analogy — just think about how painful a Charley horse is! Regardless of what’s actually going on in there, muscle pain is probably the main thing that back pain patients are feeling. The phenomenon of trigger points — tiny muscle cramps, basically11 — could be the entire problem, or a complication that’s more painful and persistent than the original problem. It’s hard to overstate how painful trigger points can be, but they are not dangerous to anything but your comfort.
In addition to these exercises, there are simple things you can do every day to help reduce your risk of hip flexor pain.  If you sit at a desk for long periods of time, try to get up and move around every hour or so.  Warm up properly before any physical activity, and stretch regularly at the end of each workout.  Your hips will thank you for it! 
A herniated disc in the back cancause sciatic like symptoms of pain that radiates from the lower back and down into the legs and calves. It can also cause pain in the butt and tail of the spine and can cause pain running down the legs and numbness in one leg. Typical symptoms include feelings of muscle weakness in the legs, sciatic nerve pain, pain in the back leg muscles, tingling in the nerves of the leg, and pain behind the knees. Treatments include ice and heat therapy, anti-inflammatory drugs, pain medications, exercise, physical therapy, steroids to decrease inflammation, and sometimes surgery.
Straight leg raise: Lie on your back with your legs straight out in front of you. Bend the knee on your uninjured side and place the foot flat on the floor. Tighten the thigh muscle on your injured side and lift your leg about 8 inches off the floor. Keep your leg straight and your thigh muscle tight. Slowly lower your leg back down to the floor. Do 2 sets of 15.

With a roster of muscles ranging from the powerful glutes to the small and agile abductors, the hips control practically all your movements. Almost every endurance athlete overworks some hip muscles while underworking others, causing severe imbalances: Runners are infamous for having weak hip adductors—the muscles on the side of the hip that help you step laterally—while cyclists tend to have massive quads and tiny glutes.
The hips are the cornerstone of every runner’s body. Comprising an array of muscle groups—from the all-powerful glutes to the smaller hip flexors and adductors—your hips propel every stride, stabilize the thighs, and (quite literally) keep the knee on the right track, physical therapist John Sauer, D.P.T., O.C.S., an endurance program manager with Athletico Physical Therapy, tells SELF.
Your best bet for losing weight anywhere — whether in your hips, abdomen, or back — of course, is to keep your nutrition in check. Instead of trying to dramatically alter your intake, Braun recommends focusing on one or two habits that you can change right away. For example, instead of grabbing a sugar-rich energy bar or drink on your way out the door in the morning, blend up a protein-packed smoothie, like Shakeology.

The problem is that these muscles aren't designed to be prime movers—they're designed to support the action of the glutes. Inability of activating the glutes can result in low back pain (low back muscles compensating), hamstring strains (overacting hamstrings), hip pain (resulting from hamstring-dominant hip extension) and knee pain (poor glute medius strength).

Resisted hip flexion: Stand facing away from a door. Tie a loop in one end of a piece of elastic tubing and put it around the ankle on your injured side. Tie a knot in the other end of the tubing and shut the knot in the door near the floor. Tighten the front of your thigh muscle and bring the leg with the tubing forward, keeping your leg straight. Return to the starting position. Do 2 sets of 15.
Gait analysis studies in the elderly show that they typically have a shortened step length. Whether that is a result of tight hip flexors or due to reduced balance, the propensity to walk with shorter steps will itself lead to tightness in hip flexors and anterior joint structures. Hip stretches may be a relatively easy preventative strategy for the elderly with gait abnormalities and may help to prevent falls.
If your hips are killing you, you probably spend a lot of time sitting—in the car, at work, on that SoulCycle seat—which puts your hips in near-constant "flexion", says Cori Lefkowith, NASM-certified personal trainer and owner of Redefining Strength in Orange County, California. Even running involves a repetitive flexion movement that can cause pain.
Low back pain commonly is experienced in the back itself. However, due to the complexity of the spinal cord and associated nerves being an intricate part of the low back, pain may and frequently can radiate or travel further down the course of the nerves. This is similar to striking your "funny bone" in the elbow and feeling the sensation in the hand below the elbow.
The more than 20 muscles that make up your hips are responsible for stabilizing your pelvis, moving your legs from side to side, and shortening to draw your knees toward your chest every time you sit down, run, jump or pedal, explains Kelly Moore, a certified yoga instructor and co-founder of Mindfuel Wellness, which brings health and wellness initiatives to companies throughout Chicago.
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.
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