Qi, L.; (2011) Use of wavelet analysis techniques with surface EMG and MMG to characterise motor unit recruitment patterns of shoulder muscles during wheelchair propulsion and voluntary contraction tasks. Doctoral thesis , UCL (University College London).

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Abstract

The high demand on the upper extremity during manual wheelchair use contributes to a high prevalence of shoulder pathology in people with spinal cord injury. The overall purpose of this thesis was to investigate shoulder muscle recruitment patterns and wheelchair kinetics in able-bodied participants over a range of daily activities and mobility tasks requiring manual wheelchair propulsion. With a complete understanding of the muscle recruitment patterns, physiotherapists and wheelchair users can improve rehabilitation protocols and wheelchair propulsion performance to prevent shoulder pathology and maintain comfort during locomotion. Motor unit recruitment patterns were examined first during isometric and isotonic contractions to determine if spectral properties from EMG and MMG could be related to the different motor units in biceps brachii by using wavelet techniques coupled with principle component analysis. The results indicated that motor unit recruitment patterns can be indicated by the spectral properties of the EMG and MMG signals. EMG activity of 7 shoulder muscles was recorded with surface electrodes on 15 able-bodied participants over a range of manual wheelchair propulsion activities. Wavelet and principle component analysis was used to simultaneously decompose the signals into time and frequency domain. There are three main conclusions that can be drawn: 1) Uphill and faster speed (1.6m/s) propulsion required higher activity levels in the shoulder muscles and greater resultant joint force than did slow speed propulsion on the ergometer (0.9m/s), thus potentially resulting in shoulder pathology. 2) Prolonged wheelchair propulsion and greater muscle activity may result in fatigue and play a factor in the development of shoulder pain and pathology over time. 3) The instructed semicircular pattern has a positive effect on shoulder muscle recruitment patterns. Further investigations need to focus on a systematic integrated data collection and analysis of kinematic, kinetic, and electromyography (EMG) data from people with spinal cord injuries.

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