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Session: Poster session I
Session starts: Thursday 24 January, 15:00

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Alessio Murgia (University Medical Center Groningen)
Hans Essers (Maastricht University Medical Centre +)
Paul Verstegen (Focal Meditech BV)
Kenneth Meijer (Maastricht University Medical Centre +)

Abstract:
Objective. To investigate the moments at the glenohumeral and elbow joints while performing daily tasks with and without using an arm support mechanism. Background. Arm support mechanisms are used to assist the movements of subjects with diverse impairments. However, the joint moments generated when using these devices during daily tasks have scarcely been investigated. Understanding how the moments change can lead to better designs by considering factors such as power, fatigue and joint loading. Methods. One healthy male participant (25 ys) performed a cyclic task consisting of reaching from the midline to a target located on his ipsilateral side at shoulder height and one shoulder width. The movement was performed with and without the SLING arm support mechanism (Focal Meditech BV). Movements were captured with an 8-camera Vicon system at 200 Hz. The SLING support force was set to give the impression of moving in a gravity-free space. Joint angles were calculated using Vicon’s inverse kinematic pipeline. An inverse dynamic analysis was also performed with the AnyBody Modeling System (AnyBody Technology). Output parameters were the net joint moments at the glenohumeral and elbow joints. Results. During the unassisted movement all the glenohumeral moments peaked when reaching the target, abduction was the highest at about 7 Nm. The elbow flexion moment varied between 1.5 and 3 Nm, reflecting the forearm’s cyclic movement. When the SLING was used, the glenohumeral abduction moment was reduced by 1 Nm, its pattern almost unchanged, while the external rotation and flexion moments were reduced by about 1.5 Nm and their patterns also changed as a result of the upward force applied by the SLING. The pattern of the elbow flexion moment remained unaltered but was reduced by about 0.5 Nm. Discussion. The moments calculated during unassisted movement were within the ranges reported in the literature for healthy subjects [1]. Using an arm support mechanism alters the moment patterns and has implications for fatigue and joint loading. At present the SLING is used to assist subjects with muscular dystrophy; future research will be focussed on using the approach described here to design better support mechanisms for this target group. REFERENCES [1] M. Nordin, M. H. Pope, and G. Andersson, Musculoskeletal Disorders in the Workplace: Principles and Practice, Mosby Inc., 2007.