Reproducibility analysis of upper limbs reachable workspace, and effects of acquisition protocol, sex and hand dominancy

None of the physical testing, nor the goniometers currently used to assess upper limb function have a high validity, sensitivity or reliability. The reachable workspace, i.e. the area covered by the farthest points a subject can reach by hand without moving his/her body, shows promise but has yet to be validated, particularly in terms of reproducibility. Therefore, this study aims to evaluate the reproducibility of the reachable workspace over a period of several weeks, and to assess the effects of two proposed acquisition protocols, as well as those of gender, and hand dominancy. Shoulder movements were recorded using a motion capture system on 10 female and 10 male healthy subjects during a random protocol, i.e. simply asking them to achieve the farthest points they could reach with their hands, and during a standardized protocol, i.e. asking them to perform predefined shoulder elevations while keeping their trunk and elbow straight. The standardized protocol was repeated 7 weeks later. Repeated measures showed no significant difference, good to excellent intraclass correlation coefficients (0.46-0.81) and small bias (0.0-1.2%). The random protocol provided significantly lower and more scattered values for the reachable workspace (80.0 ± 22.6% vs. 91.0 ± 8.1%, p = .004), whereas gender and hand-dominancy had no effect. This study showed that the reachable workspace was highly reliable over a period of 7 weeks and that both upper limbs provided similar results. It could be used to monitor various pathologies of the upper limbs and to assess treatment efficiency, using a subject's healthy limb as reference.