Test bed with force-measuring crank for static and dynamic investigations on cycling by means of functional electrical stimulation

Abstract

Cycling by means of functional electrical stimulation (FES) is an attractive training method for individuals with paraplegia. The physiological benefits of FES are combined with the psychological incentive of independent locomotion. In addition, cycling has the advantage in that the generated muscle forces are converted into drive power with relatively high efficiency compared to other means of locomotion, e.g., walking. For the design of an appropriate cycling device and the development of optimal stimulation patterns, it has to be investigated how the geometry for FES cycling, influenced by individual parameters of the FES-generated drive torques and the magnitude of variations among subjects with paraplegia, can be optimized. This study shows the design of a freely adjustable test bed with additional motor drive which allows static and dynamic measurements of force components and drive torque at the crank. Furthermore, the influence of geometry and various individual parameters on FES pedaling can be tested for each subject individually. A pedal path realized by a three-bar linkage that was optimized according to preliminary simulations further increases leg cycling efficiency. Safety precautions avoid injuries in case of excessive forces, e.g., spasms. Test results illustrate the application of the test bed and measurement routines. A test series with four paraplegic test persons showed that the presented static and dynamic measurement routines allow to provide optimal stimulation patterns for individual paraplegic subjects. While pedaling with these optimal stimulation patterns only negligible negative active drive torques, due to active muscle forces, were applied to the crank and sufficient drive power was generated to power a cycle independently.

Comparison of stimulation patterns for FES-cycling using measures of oxygen cost and stimulation cost

“…This approach is based upon a dynamic simulation model of lower-limb cycling, and has not thus far been experimentally verified. Alternatively, Gföhler et al [25] have empirically measured output forces in response to stimulation over large angle ranges, and have used these results to choose desirable activation ranges.…”

Can the efficacy of electrically stimulated pedaling using a commercially available ergometer BE improved by minimizing the muscle stress–time integral?

“…These modifications did not result in increased power output in untrained subjects. In another set of studies designed to maximize pedaling power, Gföhler et al 53 determined subject-specific stimulation patterns using an adjustable FES pedaling ergometer, and Trumbower and Faghri 27 identified timing patterns based on EMG recordings of neurologically intact subjects pedaling an ERGYS ergometer. To our knowledge, the timing patterns from these studies have not been tested experimentally.…”

Isokinetic Cycling and Elliptical Stepping: A Kinematic and Muscle Activation Analysis

“…Numerous studies have been conducted to provide insight into the clinical efficacy of cycling exercise for the improvement of leg muscle function and coordination [1][2][3][4][5].…”