Trunk and glenohumeral joint adaptations to manual wheelchair propulsion over a cross-slope: An exploratory study.

Background: Cross-slopes are often encountered by manual wheelchair users propelling within an urban setting. While propulsion over cross-slopes is more difficult than on level surfaces, little is known about how the users counter the downhill turning tendency of the wheelchair over cross-slopes. This study aimed to identify the adaptations of the manual wheelchair users to the presence of cross-slopes and examine how these might impact shoulder injury.

Methods: Nine manual wheelchair users propelled themselves across a cross-slope and over a level surface. The trunk and glenohumeral joint kinematics, as well as the handrim contact tangential force were compared between both conditions for the uphill and downhill limbs.

Findings: The uphill arm technique used to counter the downhill turning tendency varied greatly in terms of potential injury risk and efficiency between participants. Trunk flexion increased the turning tendency of the manual wheelchair, yet only one participant decreased his flexion when rolling over the cross-slope. Various potential pathomecanisms related to the trunk lateral flexion and the glenohumeral kinematics over a cross-slope were identified.

Interpretation: Both the uphill arm technique and trunk kinematics are important to propel over a cross-slope both efficiently and safely. Accordingly, tips about posture and kinematics are needed to teach this skill to manual wheelchair users. Additionally, as wheelchair positioning seems to influence the cross-slope skill, more research is needed to explore the impact of positioning devices (e.g., lateral supports) and wheelchair modifications (e.g., power assist wheels, handrim projections) on this skill.