This method became quite popular as a desired hair growth trigger since the encouragement of blood flow to the scalp and roots is thought to help trigger hair growth. The basic requirement is that you put your head below your heart to encourage the blood flow which may stimulate hair growth. Inversion hair growth methods can be as simple as laying on a bed with your head extended off one side or as complicated as strapping into an official body inversion machine and hanging completely upside down. Some yoga poses, such as the headstand, also encourage blood flow to the brain.
Before undertaking an Inversion techniques always check with your primary health care physician to make sure there is no reason you shouldn't be encouraging blood flow to your scalp and brain by hanging upside down.