Relationship Between Shoulder Pain and Kinetic and Temporal-Spatial Variability in Wheelchair Users

Objective: To examine intra-individual variability of kinetic and temporal-spatial parameters of wheelchair propulsion as a function of shoulder pain in manual wheelchair users (MWUs). Design: Cohort. Setting: University research laboratory. Participants: Adults with physical disabilities (N=26) who use a manual wheelchair for mobility full time (>80% ambulation). Interventions: Participants propelled their own wheelchairs with force-sensing wheels at a steady-state pace on a dynamometer at 3 speeds (self-selected, 0.7m/s, 1.1m/s) for 3 minutes. Temporal-spatial and kinetic data were recorded unilaterally at the hand rim. Main Outcome Measures: Shoulder pain was quantified with the Wheelchair Users Shoulder Pain Index. Intra-individual mean, SD, and coefficient of variation (CV=mean/SD) with kinetic and temporal-spatial metrics were determined at the handrim. Results: There were no differences in mean kinetic and temporal-spatial metrics as a function of pain group (P values >.016). However, individuals with pain displayed less relative variability (CV) in peak resultant force and push time than pain-free individuals (P<.016). Conclusions: Shoulder pain had no influence on mean kinetic and temporal-spatial propulsion variables at the handrim; however, group differences were found in relative variability. These results suggest that intra-individual variability analysis is sensitive to pain. We propose that variability analysis may offer an approach for earlier identification of MWUs at risk for developing shoulder pain. (C) 2014 by the American Congress of Rehabilitation Medicine