Comparison between overground and dynamometer manual wheelchair propulsion

Abstract

Laboratory-based simulators afford many advantages for studying physiology and biomechanics; however, they may not perfectly mimic wheelchair propulsion over natural surfaces. The goal of this study was to compare kinetic and temporal parameters between propulsion overground on a tile surface and on a dynamometer. Twenty-four experienced manual wheelchair users propelled at a self-selected speed on smooth, level tile and a dynamometer while kinetic data were collected using an instrumented wheel. A Pearson correlation test was used to examine the relationship between propulsion variables obtained on the dynamometer and the overground condition. Ensemble resultant force and moment curves were compared using cross-correlation and qualitative analysis of curve shape. User biomechanics were correlated (R ranging from 0.41 to 0.83) between surfaces. Overall, findings suggest that although the dynamometer does not perfectly emulate overground propulsion, wheelchair users were consistent with the direction and amount of force applied, the time peak force was reached, push angle, and their stroke frequency between conditions.

Figure 1

Moment about the hub for dynamometer (solid line) and tile (dashed line) for various correlation coefficients. The highest correlations are seen for curves with similar curve types and magnitudes (A). Panel (B) shows curves with similar slopes but different magnitudes. The lowest correlation is seen between different curve types (C); however, it can be noted that the slope of the final decrease in moment is similar between surfaces.

Figure 2

Representative curves for bimodal, unimodal, and flat curve types. Distinct peaks can be seen in the bimodal and unimodal curves. A characteristic level region can also be seen with the flat curve type.

Figure 3

Distribution of moment about the hub curve types across conditions.