Groin muscles can be tricky. There are multiple reasons for tight groins, but one can be your chronically weak gluteus medius. This causes something called altered reciprocal inhibition or ARI. When one muscle is too weak, the antagonist (the muscle that does the opposite action) becomes too tight.

So, for the groin, the adductors are the antagonists of the gluteus medii. If the glute medius is weak, the adductors tighten up. If the gluteus medii is tight, the adductors become weak.

Stretching your groin can be hard because most lifters are too tight in other areas (hamstrings, hip flexors and thoracic spine) to be able to access many of the groin stretches available. As a result, you can't even "reach" your groin muscles to stretch them in the first place.

Stretching your groin isn't going to fix the problem entirely, but this will certainly help:

1. Grab a pillow, towel or anything that's roughly 2-4 inches high, depending on your flexibility – shorter if you're more flexible, higher if you're not very flexible. Put your butt at the edge of your prop and let your pelvis tilt forward slightly.
2. Bring your legs to a wide-legged position. Make them wide enough to feel a stretch, but nothing extreme. Think a 5 on a stretch scale of 1-10.
3. Point your toes up to the ceiling and dig your heels into the ground. Bring your fingers out in front of you.
4. Now pull your ribcage back as if someone had their hands around you from behind and was pulling your torso back. Another way to think of this is to arch your mid-lower back.
5. Re-walk your fingers out in front of you until you feel a slight stretch in your inner thigh. Keep an arch in your back. Breathe and hold for 1-2 minutes.
6. Don't snap out of the stretch. When you're done, slowly sit up, bring your hands under your knees and move your legs back together with your hands.