Effects of Functional Electrical Stimulation on Trunk Musculature during Wheelchair Propulsion

During wheelchair propulsion, in order to apply power to the pushrim effectively, shoulder and trunk stabilization is needed to control arm movements and the consequent transfer of power from the limbs through to the pushrim. Available trunk control may be one of the most important force-generating mechanisms during wheelchair propulsion, particularly when an individual is fatigued or propelling through a demanding situation. Consequentially it is a worthwhile pursuit to further understand and study the process of trunk muscle recruitment during propulsion and the effects of reduced trunk control on propulsion biomechanics. In the first of three studies contained in this dissertation is, trunk muscle recruitment patterns using surface electromyography (sEMG) electrodes during wheelchair propulsion under different speed conditions. The results of this first study provided insight into the functional role of specific trunk muscles during propulsion.In the second study, a biomechanical analysis was utilized to examine the effect of functional electrical stimulation (FES) on trunk musculature during five minutes of wheelchair propulsion. The findings revealed that a trunk FES device could help an individual to generate more propulsion power and increase gross mechanical efficiency during wheelchair propulsion. Consequentially, a user with a trunk FES device may be able to more easily negotiate demanding propulsion tasks, ultimately improving quality of life. The third study investigated the influence of surface electrical stimulation of trunk musculature on shoulder muscle recruitment patterns during wheelchair propulsion. The results showed that trunk FES may help individuals to generate wheelchair propulsion power without placing additional demands on shoulder musculature. With trunk stimulation, the functional role of the shoulders may shift from stabilizers to a prime movers contributing more directly to propulsion.In the future, improvements can be made with advanced programming. A FES device could be better synchronized with the propulsion cycle to avoid continuous stimulation causing muscle fatigue. It would be ideal to provide stimulation during pre-push and early push phase of the propulsion cycle when trunk stability has been shown to be most critical. Individuals could potentially benefit from using FES more during challenging tasks of short duration, such as pushing up a ramp.