Advanced 1-Leg Hamstring/Inner Thigh/Groin Stretch
This stretch involves stretching one leg at a time and having the leg you are stretching elevated on an object. You can use things like a chair, couch, step, table, or whatever you have available.
During this stretch, you will change the position of your feet and body, in order to change the area you are stretching. When your heel is on the object and your toes are pointing up or forward, the focus is on the hamstring.
You can increase the stretch by rotating your hips back (anterior pelvic tilt) or moving your center of gravity down and away from the stretching leg.
If you turn the foot of the stretching leg so the inside of your foot is flat on the object, the stretch focuses on the inner thigh/groin area. For example, if you are stretching your left hamstring (left foot elevated), rotate your left foot and leg to the right.
You will probably have to move your other leg to maintain correct body alignment. When done correctly, both feet and knees should basically be pointing in the same direction.
This stretch can be intensified by tilting your pelvis away from the stretching leg. If stretching the left inner thigh, raise your right hip and lower your left one. You can also move your center of gravity down and away from the stretching leg or moving the non-stretching leg further away from the stretching one.
When doing this stretch, make sure the pull is centered on the inner thigh and not the knee. If you feel discomfort or stress in the knee, then change your position to move the focus of the stretch back to the muscles, instead of the joint.
This stretch can help you work up to doing full side splits or box splits, if you don’t have the flexibility to do them yet.