A Novel Treadmill That Can Bilaterally Adjust the Vertical Surface Stiffness

Surface stiffness plays an important role in human locomotion mechanics and can affect both the energy expenditure and the gait of human. In order to be able to systematically analyze these effects, this paper presents the design and development of a novel treadmill with the ability to regulate stiffness of the surface. The novelty of the system is on its stiffness adjustment mechanism that can achieve: First, purely vertical displacement of the surface, second, wide range of stiffness regulation, third, bilateral stiffness regulation for the left and the right legs, independently, and fourth, consistent stiffness of the surface, independent of the location of the person on the treadmill. The presented system is a unique tool to systematically study the effect of surface compliance on the metabolic cost and the dynamics of human walking. This can also introduce new rehabilitation strategies for mobility impaired patients. In order to show the proof of concept, we also present preliminary experiments to show the effect of surface stiffness regulation on the metabolic cost and gait of a healthy subject.