Bullworkers, Tensolators.

http://www.renaissanceexercise.com/the-future-of-exercise/

Still not sure if these work....

Bruce Lee used Bullworker exercises to increase his punching power and speed.
Bruce, stopped using free weights after injuring himself performing an exercise called “Good Mornings.” He began using an isometric power rack as well as the Tensolator or Bullworker along with free hand isometrics and bodyweight exercises to help keep him in his incredible physical conditioning.

 http://www.bullyextreme.com/2013/08/bullworker-exercises/

Not positive if this is so, perhaps..Reviews amazon