e130 Friday 17 October Papers / Journal of Science and Medicine in Sport 18S (2014) e108–e135

mental data to drive simulations of muscle-tendon dynamics andenergetics. Using a musculoskeletal model developed in OpenSimsoftware we predicted muscle-tendon dynamics for MG, LG, SO andTA with and without exoskeletons. These dynamics then servedas inputs to a model of muscle energetics that calculated musclemetabolic energy consumption.

Results and discussion: Experimental results showed thatexoskeletons effected a reduction in muscular contributions toankle joint kinetics, reduced SO EMG and whole body net metabolicpower. Paradoxically, exoskeletons did not reduce SO fasciclemechanical work owing to a trade-off between increased fasci-cle length change and decreased SO forces. The modeling resultsshowed no significant reduction in PF energy consumption withexoskeletons despite reductions in PF muscle forces. The simu-lations showed exoskeletons to increase PF fiber velocities andshift PF operating lengths to shorter and less optimal lengths. Thisresulted in less-favourable conditions for muscle force productionand explained the lack of reduction in PF energy consumption withexoskeletons.

http://dx.doi.org/10.1016/j.jsams.2014.11.110

Symposium

53

Factors contributing to the mechanical demandimposed on the upper extremity during manualwheelchair propulsion

J. McNitt-Gray 1,∗, J. Munaretto 1, S. Raina 1,I. Russell 1, P.S. Requejo 2

1 Departments of Biological Sciences and BiomedicalEngineering, University of Southern California, LosAngeles, CA, USA2 Rancho Los Amigos National Rehabilitation Center,Downey, CA, USA

Introduction: Repetitive mechanical loading of the shoulderduring manual wheelchair (WC) propulsion has been associatedwith disabling shoulder pain that can significantly affect healthand active community particularly for those with spinal cordinjury (SCI). Previous efforts have sought to reduce the mechan-ical demand imposed on the upper extremity of manual WC usersvia WC design and reduction in load exposure. For example, modifi-cations in materials and WC construction significantly reduces themass of the WC, thereby reducing the magnitude of the tangen-tial component of the reaction force (RF) needed to maintain WCspeed. Adjustable WC components also provide multiple solutionsfor reconfiguring the WC to achieve a recommended seated posture,stability, and elbow extension angle when the hand is at top-dead-center of the handrim. Load exposure experienced by the WC useris known to be affected by pushing frequency and the mechanicalload experience during each propulsive cycle. Clinical research hasshown that increasing the duration of hand contact may reduce theaverage force, but not necessarily peak reaction forces (RF) dur-ing the impact or propulsive phases. Furthermore, experimentalshoulder joint kinetics during manual WC propulsion have beenreported to vary considerably between individuals and in differentWC seating configurations. The aim of this paper is to discuss howthe orientation of the RF relative to the upper extremity segments

and adjacent joint moments influence the magnitude and distribu-tion of mechanical demand imposed on the upper extremity duringmanual WC propulsion at different speeds and conditions.

http://dx.doi.org/10.1016/j.jsams.2014.11.111

54

Enhancing the athlete interface forperformance impact in wheelchair tennis

K. Faulkner

Australian Paralympic Committee, Australia

Background: Wheelchair tennis athletes use their chair formobility around the court and as a stable base over which theyplay their shot. These competing demands require maximum con-trol of equipment. It was hypothesized that increasing conformity,enhancing surface materials and maximising the total area ofathlete-chair interface would benefit acceleration, mobility andpower of the shot.

Method: 3 high performance wheelchair tennis athletes wereprovided with a prototype customised interface which they wereable to interchange with their regular seat. They trained with theprototype for a period of 4 weeks following which time subjectiveand objective performance data was recorded. The control test usedtheir original cushion both at baseline and after the 4 week trial.

Results: While subjective feeback was strong and the playersand coach preferred the customised seat, this was not reflected inskills tests which demonstrated very little difference between theinterfaces.

Discussion: In theory, customising the interface in wheelchairtennis is a sound principle. Skill-based testing needs to be furtherexplored in an effort to increase sensitivity of objective testing. Atthis stage, performance benefits have not been demonstrated inthis small case study.

http://dx.doi.org/10.1016/j.jsams.2014.11.112

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Wheelchair propulsion and shoulder postureconsiderations in quadriplegic athletes

K. Faulkner

Australian Paralympic Committee, Australia

Background: In wheelchair sport, the incidence of shoulder painis reported to be as high as 70%. The shoulder is loaded throughwheelchair propulsion, throwing, prolonged sitting posture andtransfers. The primary challenge to the physiotherapist is not tofind the diagnosis but to address the contributing factors while res-pecting the constraints of the sporting and every-day environment.

Discussion: Athletes participating in Wheelchair Rugby arequadriplegic or 4-limb affected amputees. The Sports Physiother-apy team can have a role in performance optimisation throughthe identification of ideal shoulder posture for propulsion in eachindividual athlete. This presentation will outline the steps the Aus-tralian team has taken in consideration of shoulder posture forquadriplegic athletes.

http://dx.doi.org/10.1016/j.jsams.2014.11.113