Hyperbolic Stretching is the name of a stretching program designed by Alex Larsson who markets himself as a flexibility and core strength expert but his credentials can't actually be found online.

His program combines several methods of stretching including a form of pnf stretching. With this type of stretching you use your reflexes to help you get a deeper stretch to improve flexibility. He also includes dynamic stretches also called active stretches and some Hyperbolic Stretching program as well.

According to the website the program relies on three principles to help improve flexibility. The first is called inverse survival reflex which is really the pnf concept of hold-relax. With this concept you put the muscle in a stretched position and contract the muscle without moving isometrically which then triggers a reflex that allows you to move deeper into the stretch.

To picture the first principle imagine a lying hamstring stretch with a partner. Your partner pushes against the back of your calf and ankle and at the same time you push back against their resistance. Then you relax your leg allowing the partner's gentle push to deepen your stretch.

Technically outside of the program the second principle is s. A. I. D. Or specific adaptation to imposed demands. Basically this means if you want to do the splits you need to actually practice stretches that mimic this motion.