A Novel Application of Eddy Current Braking for Functional Strength Training During Gait

Abstract

Functional strength training is becoming increasingly popular when rehabilitating individuals with neurological injury such as stroke or cerebral palsy. Typically, resistance during walking is provided using cable robots or weights that are secured to the distal shank of the subject. However, there exists no device that is wearable and capable of providing resistance across the joint, allowing over ground gait training. In this study, we created a lightweight and wearable device using eddy current braking to provide resistance to the knee. We then validated the device by having subjects wear it during a walking task through varying resistance levels. Electromyography and kinematics were collected to assess the biomechanical effects of the device on the wearer. We found that eddy current braking provided resistance levels suitable for functional strength training of leg muscles in a package that is both lightweight and wearable. Applying resistive forces at the knee joint during gait resulted in significant increases in muscle activation of many of the muscles tested. A brief period of training also resulted in significant aftereffects once the resistance was removed. These results support the feasibility of the device for functional strength training during gait. Future research is warranted to test the clinical potential of the device in an injured population.

Reliable sagittal plane kinematic gait assessments are feasible using low-cost webcam technology

“…Further, the clinical utility of webcam-based motion tracking is high as only minimal expertise is required to operate this system. The real-time processing of kinematic data also allows for the provision of kinematic biofeedback, which could be useful in facilitating therapeutic outcomes [11, 12]. For these reasons, webcam-based motion tracking can serve as a suitable alternative when 3D systems are unavailable.…”

A Semi-passive Planar Manipulandum for Upper-Extremity Rehabilitation

“…We note that this list is not exhaustive, and other types of brakes (e.g., eddy current brakes) could have been applied. 43 The magnetic particle brakes were chosen for this application because they are of moderate cost and provide a feeling similar to dry friction, which is a more predictable force profile. Additionally, they are under direct electronic control and have actuation times similar to smart fluid brakes (14 ms), however there is some hysteresis in the torque profile of the brake.…”

A Portable Passive Rehabilitation Robot for Upper-Extremity Functional Resistance Training

“…There are numerous passive actuators that could provide scalable resistance for a robotic device. We selected custom miniature passive eddy current brakes to act at each of the robot's joints [45]. Eddy current brakes are a low-cost and easily scalable method for providing viscous (i.e., velocity dependent) resistance.…”

“…For eddy current disc brakes, the resistive torque, τ, is determined by the following equation: [45], [53], [54]…”