1 JRRD JRRD Volume 50, Number 5, 2013 Pages ???–??? Coordination patterns of shoulder muscles during level-ground and incline wheelchair propulsion Liping Qi, PhD; 1–2 James Wakeling, PhD; 3 Simon Grange, PhD; 1–2 Martin Ferguson-Pell, PhD 2* 1 ASPIRE Centre for Disability Sciences, Institute of Orthopedics and Musculoskeletal Science, University College London, Brockley Hill, Stanmore, London, United Kingdom; 2 Faculty of Rehabilitation Medicine, University of Alberta, Edmonton, Alberta, Canada; 3 Department of Biomedical Physiology and Kinesiology, Simon Fraser Univer- sity, Burnaby, British Columbia, Canada Abstract—The aim of this study was to investigate how the coordination patterns of shoulder muscles change with level- ground and incline wheelchair propulsion. Wheelchair kinetics and electromyography (EMG) activity of seven muscles were recorded with surface electrodes for 15 nondisabled subjects during wheelchair propulsion on a stationary ergometer and wooden ramp (4 degree slope). Kinetic data were measured by a SmartWheel. The kinetics variables and the onset, cessation, and duration of EMG activity from seven muscles were com- pared with paired t-tests for two sessions. Muscle coordination patterns across seven muscles were analyzed by principal com- ponent analysis. Push forces on the push rim and the percent- age of push phase in the cycle increased significantly during incline propulsion. Propulsion condition and posture affected muscle coordination patterns. During incline propulsion, there was more intense and longer EMG activity of push muscles in the push phase and less EMG activity of the recovery muscles, which corresponded with the increased kinetic data total force output and longer push phase in the incline condition. This work establishes a framework for developing a performance feedback system for wheelchair users to better coordinate their muscle patterning activity. Key words: electromyography, ergometer, kinetics, muscle synergy, principal component analysis, propulsion, rehabilita- tion, shoulder, wavelet analysis, wheelchair. INTRODUCTION People with spinal cord injury (SCI) usually rely on their ability to propel a manual wheelchair for indepen- dent mobility [1]. Achieving the highest degree of inde- pendence in a manual wheelchair often depends on the user’s ability to negotiate a range of environments and overcome indoor and outdoor obstacles. Ramps of vary- ing degrees are frequent both outdoors and indoors. Labo- ratory investigations have revealed that shoulder joint forces [2–4] and muscle demands [5] are greater during incline propulsion than during level-ground propulsion. Wheelchair users also adopt different postures and employ different stroke techniques to suit different loco- motion tasks [6]. When moving up a ramp, they tend to lean forward more than when rolling along a level surface, Abbreviations: AD = anterior deltoid, BB = biceps brachii, EMG = electromyography, MD = middle deltoid, ME = mechanical effectiveness, MVC = maximum voluntary isomet- ric contraction, PC = principal component, PCA = principal component analysis, PD = posterior deltoid, PM = pectoralis major, SCI = spinal cord injury, sEMG = surface electromyog- raphy, TB = triceps brachii, UT = upper trapezius. * Address all correspondence to Martin Ferguson-Pell, PhD; 3-48 Corbett Hall, University of Alberta, Edmonton, Alberta, Canada T6G 2G4; 780-248-1367; fax: 780-492- 1626. Email: martin.ferguson-pell@ualberta.ca http://dx.doi.org/10.1682/JRRD.2012.06.0109