In Rolfing® Structural Integration, we have a classic 10-Session Series that I tell my Seattle clients to think of as a 50,000-mile tune-up on their bodies: it's a very thorough protocol to align and balance the body in gravity, strategized and tailored for each person. One of my favorite sessions of the Series is the 4th session, where we work the inner line of the leg to increase leg swing and connect a sense of lift from the arch of the foot to the pelvic floor – a mysterious connection that relates to Ida Rolf's axiom that gravity will lift an aligned body, rather than drag it down.
Among the key structures of the inner leg are the adductors – a group of muscles between the quadriceps group in the front and the hamstring group in the back. The adductors connect onto the pelvis at their upper end, and when tight can "drag" on it, and through the pelvis drag on the spine, contributing to low-back pain.
When contracted, the adductors bring your legs together. When relaxed, they allow your legs to spread. Now watch the video below.
For your legs to go into the splits like Jean-Claude Van Damme does here, you have to have good adductor length - as well as superb control to gradually let the muscles go. [Any of you who do Pilates reformer work will know this from the move where you have one foot stabilized on the frame, and the other on the unfixed carriage, using the adductors to bring the carriage in and slowly release it out.]
Most people can't do the splits because their adductors are too shortened, and unfortunately these muscles are neglected in most people's stretching programs. An exception to this is martial artists, and I think it's no accident that Van Damme is a martial artist. If you are going to do any kicks into the air and moves like that, you need adductor length, and you need your adductors to have fascial glide relative to the quads and hamstrings. In most human beings who are not martial artists or dancers, the adductors are shortened – dragging on the pelvis – and bound up with either the quads or the hamstrings or both. A session with a Rolfer™ can help free and lengthen your adductors, resulting in much more mobility (a longer stride for runners), which often helps to relieve low-back pain as each step you take is no longer dragging on your pelvis.
And of course Van Damme shows amazing self-possession and centering here. He's clearly trained his mind and emotions, not just his body.