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 (MWU). Design Cohort Setting University Research Laboratory Participants 26 adults with physical disabilities 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 (WUSPI). Intra-individual mean, standard deviation (SD), and coefficient of variation of (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's > 0.016). However, individuals with pain displayed less relative variability (CV) in peak resultant force and push time then pain free individuals (p<0.016). 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. It is proposed that variability analysis may offer an approach of earlier identification of manual wheelchair users at risk for developing shoulder pain.

Background Manual wheelchair users report a high prevalence of shoulder pain. Growing evidence shows that variability in forces applied to biological tissue is related to musculoskeletal pain. The purpose of this study was to examine the variability of forces acting on the shoulder during wheelchair propulsion as a function of shoulder pain. Methods Twenty-four manual wheelchair users (13 with pain, 11 without pain) participated in the investigation. Kinetic and kinematic data of wheelchair propulsion were recorded for three minutes maintaining a constant speed at three distinct propulsion speeds (fast speed of 1.1 m/s, a self-selected speed, and a slow speed of 0.7 m/s). Peak resultant shoulder forces in the push phase were calculated using inverse dynamics. Within individual variability was quantified as the coefficient of variation of cycle to cycle peak resultant forces. Findings There was no difference in mean peak shoulder resultant force between groups. The pain group had significantly smaller variability of peak resultant force than the no pain group (p < 0.01, η2 = 0.18). Interpretation The observations raise the possibility that propulsion variability could be a novel marker of upper limb pain in manual wheelchair users.

BackgroundMonitoring physical activity and leveraging wearable sensor technologies to facilitate active living in individuals with neurological impairment has been shown to yield benefits in terms of health and quality of living. In this context, accurate measurement of physical activity estimates from these sensors are vital. However, wearable sensor manufacturers generally only provide standard proprietary algorithms based off of healthy individuals to estimate physical activity metrics which may lead to inaccurate estimates in population with neurological impairment like stroke and incomplete spinal cord injury (iSCI). The main objective of this cross-sectional investigation was to evaluate the validity of physical activity estimates provided by standard proprietary algorithms for individuals with stroke and iSCI. Two research grade wearable sensors used in clinical settings were chosen and the outcome metrics estimated using standard proprietary algorithms were validated against designated golden standard measures (Cosmed K4B2 for energy expenditure and metabolic equivalent and manual tallying for step counts). The influence of sensor location, sensor type and activity characteristics were also studied.Methods28 participants (Healthy (n = 10); incomplete SCI (n = 8); stroke (n = 10)) performed a spectrum of activities in a laboratory setting using two wearable sensors (ActiGraph and Metria-IH1) at different body locations. Manufacturer provided standard proprietary algorithms estimated the step count, energy expenditure (EE) and metabolic equivalent (MET). These estimates were compared with the estimates from gold standard measures. For verifying validity, a series of Kruskal Wallis ANOVA tests (Games-Howell multiple comparison for post-hoc analyses) were conducted to compare the mean rank and absolute agreement of outcome metrics estimated by each of the devices in comparison with the designated gold standard measurements.ResultsThe sensor type, sensor location, activity characteristics and the population specific condition influences the validity of estimation of physical activity metrics using standard proprietary algorithms.ConclusionsImplementing population specific customized algorithms accounting for the influences of sensor location, type and activity characteristics for estimating physical activity metrics in individuals with stroke and iSCI could be beneficial.Electronic supplementary materialThe online version of this article (10.1186/s12984-018-0358-y) contains supplementary material, which is available to authorized users.

Manual wheelchair users are at great risk for the development of upper extremity injury and pain. Any loss of upper limb function due to pain adversely impacts the independence and mobility of manual wheelchair users. There is growing theoretical and empirical evidence that fluctuations in movement (i.e., motor variability) are related to musculoskeletal pain. This perspectives paper discusses a local review on several investigations examining the association between variability in wheelchair propulsion and shoulder pain in manual wheelchair users. The experimental data reviewed highlights that the variability of wheelchair propulsion is impacted by shoulder pain in manual wheelchair users. We maintain that inclusion of these metrics in future research on wheelchair propulsion and upper limb pain may yield novel data. Several promising avenues for future research based on this collective work are discussed.