Good article. The comment section mentions Roger Teeter and EP skis. In 1981 Roger Teeter designed his Teeter Inversion machine.
http://www.teeter-inversion.com/teeter-MessagefromRoger.asp
My wife and I started Teeter Hang Ups® in my forties as a result of my own journey to find relief from back pain. At the time, I was designing waterskis and competing at a national level, though my back pain was so severe that I was forced to wear a steel reinforced lace-up brace every time I skied. Through other competitive skiers, I was introduced to Gravity Boots and for the first time I was pain free. The relief was not just the result of silencing symptoms; inversion was actually targeting the source of the ache. As an engineer, I knew I found my calling--to design and manufacture inversion equipment so that more people could take control of their health and find natural, sustainable relief.