Validation of a biofeedback system for wheelchair propulsion training

Abstract

This paper describes the design and validation of the OptiPush Biofeedback System, a commercially available, instrumented wheel system that records handrim biomechanics and provides stroke-by-stroke biofeedback and targeting for 11 propulsion variables. Testing of the system revealed accurate measurement of wheel angle (0.02% error), wheel speed (0.06% error), and handrim loads. The maximum errors in static force and torque measurements were 3.80% and 2.05%, respectively. Measured forces were also found to be highly linear (0.985 < slope < 1.011) and highly correlated to the reference forces (r(2) > .998). Dynamic measurements of planar forces (F(x) and F(y)) and axle torque also had low error (-0.96 N to 0.83 N for force and 0.10 Nm to 0.14 Nm for torque) and were highly correlated (r > .986) with expected force and torque values. Overall, the OptiPush Biofeedback System provides accurate measurement of wheel dynamics and handrim biomechanics and may be a useful tool for improving manual wheelchair propulsion.

Figure 1

The components (a) and assembly (b) of the OptiPush wheel.

Figure 2

Definition of the stroke cycle, push phase, and coast phase.

Figure 3

Example of the push-by-push biofeedback display.

Figure 4

Centrifugal force (F _C) and gravitation (F _G) force of the test mass applied to the handrim during dynamic testing, where θ is the wheel angle, ω is the angular velocity of the wheel, r is the radius of the handrim, and α is the angle of the mass with respect to the load cell coordinate system.