Here are some simple Hip Flexor exercises and stretches if you have a strain or pain in your hip flexors.
Start off standing, and get next to something sturdy you can hold onto for balance. This will stretch your hip flexor and your quad. Grab the ankle of the side you want to stretch and pull it behind you. If you don’t have enough flexibility to grab it, you can use a belt or strap to pull it up towards you. Try to keep your upper body vertical, and don’t lean forward. If you lean forward, you won’t feel the stretch. Also make sure your thigh is either even with the other side or slightly behind the other side to get the full stretch. Pull your leg backwards and up until you feel a stretch. Hold this for 30 seconds and do it three times.
Next is a hip flexor stretch in a lunge position. First start in a kneeling position. Place the knee of the hip flexor you want to stretch on the ground, and take the opposite leg and bend it in front of you at a ninety-degree angle. You might want to place a pillow under your knee to protect it. You will be in a lunge position with the knee of your injured side on the ground. Now drive the knee of the uninjured side forward away from your body. Hold for 30 seconds, and do this 3 times. If you want to stretch the groin as well, take the good side, and put it out at a 45 degree angle away from your body, then lunge towards that angle.
Now for the strengthening, lie down on your back. Bend the knee up on the good side for support. Then simply slide the bad side up and down, keeping your foot on the ground. If that is easy, you can do a straight leg raise (SLR). You want to squeeze your muscles tight to lock out the knee and pull your toes towards your head to keep the whole leg straight. This will work your hip flexor muscles when you lift your leg off the ground. Use slow controlled movements to make sure you are using the muscles and not momentum. Start off with ten, and work your way up.
Finally, you can do resistive exercises standing up. Using a resistive band, wrap it around something sturdy. Wrap the band around either leg. You will do the exercises on both legs. The leg that has the band on it is working dynamically or with movement. The other leg is working statically to keep you stable. You will keep your leg straight and try not to bend your knee. Turn away from where the band is anchored, it kick forward. You don’t have to kick high, just keep it controlled with your knee locked out.