Question

Produces significant force without any considerable changes in the leght of the muscle

Answer 1

ITS NON CONTACT FORCE BUDDY

Answer 2

The BOSU Elite was created to provide a significant feedback force to the muscles from its high density dome without lengthening the muscle. David Weck (inventor) discovered the incredible benefit of muscular isometric contraction against the forces of the high density dome. The more force the trainee can exert the greater the resistance force from the dome. This has a profound effect both internally and externally on the body. For more info check out this article I wrote. Peak Athletic Performance with the BOSU Elite | Functional Strength This kind of training can significantly improve posture and athletic functionality.