Chapter 7 - TwAS: treadmill with adjustable surface stiffness

Abstract

In biomechanics of human locomotion, the physical properties of the walking surface are important factors that can affect the kinematics and dynamics as well as the energy requirement of the locomotion. Softness of the surface is a critical factor when it comes to rehabilitation applications for mobility impaired patients. Many poststroke patients are prescribed to walk on a compliant surface such as foam walkways to better prepared them for the real-world scenarios such as walking on grass, mud, etc. However, and while the softness of foam walkways is not adjustable, the best level of surface stiffness differs from one patient to another, and even for one individual patient the best level of surface stiffness changes as the rehabilitation process progresses. Furthermore, during the initial stages of rehabilitation for mobility impaired patients, partially canceling the weight is another important factor as many of these patients are not able to support their own weight during walking. This chapter presents a novel dual belt Treadmill with Adjustable Stiffness (TwAS) where speed and surface stiffness of each belt can be independently adjusted based on what is best for a particular user. In addition, the TwAS treadmill is integrated with the following systems: a weight cancelation hydraulically actuated harness system LiteGait, motion capture system with eight Vicon cameras, and a ParvoMedics VO2max metabolic cost measurement system. With this integrated system, a mobility impaired patient can walk at different speeds, on different surface stiffness levels while the walking kinematics can be tracked by the motion capture system and the energy expenditure can be measured by the VO2max system. Furthermore, using the model-based surface stiffness level together with the tracked surface deflection using the motion capture system, the ground reaction force can be calculated which can be used to understand the joints’ torques through inverse dynamic approaches. This system can provide a unique rehabilitation and evaluation platform for the therapist as it can provide real-time data on the performance of mobility impaired patients. This system is also a valuable tool for rehabilitation of injured athletes.