M.Tech. (Chiropractic) / The purpose of this study was to establish whether cervical spinal manipulation induces an appreciable and sustainable alteration in muscle torque performance regarding the elbow flexor muscles. Forty asymptomatic individuals participated in this study. Twenty individuals were randomly assigned to either an experimental or control group. Participants selected had to be between 18 and 40 years of age and had to present with cervical motion restrictions involving the fourth to sixth cervical vertebrae, as determined by motion palpation assessment. Participants were randomly recruited from the University of Johannesburg and surrounding areas, based on their response to information pamphlets and word of mouth. The experimental group received cervical spinal manipulation involving the lower cervical segments on three separate occasions. The control group received no intervention. Elbow flexion torque assessments were conducted using the Biodex System 3, isokinetic dynamometer. Two assessments were done prior to intervention and one test following one week of intervention, to ascertain whether cervical manipulation can provoke a sustainable improvement in elbow flexion performance. Cervical range of motion (CROM) assessment was used as a secondary objective evaluation to assess the effectiveness of the manipulation procedures, considering that improvement in cervical range of motion following spinal manipulation is well documented. Minimal improvement in elbow flexion torque involving both arms was observed in the experimental group following one weeks‟ intervention however, no statistical significance was reported. Gender relations regarding the elbow flexion torque performances revealed and improvement in strength in the male participants and a reduction in performance in the female participants. Statistical significance was reported although the significance regarding intervention remains unclear. No sustainable improvement in elbow flexion torque was revealed following spinal manipulative therapy and therefore does not provide conclusive evidence to substantiate the motor neuron excitability theory. The contradictory results with regards to the female participants bring into context an indefinite and unfamiliar neuromusculoskeletal paradigm which requires additional research to clarify these anomalous findings.

Empirical and modelling studies are reported which explore ways in which the central nervous system might consider musculo-skeletal geometry when generating commands for single degree of freedom elbow flexion and extension movements. In a series of experiments it is shown that subjects do not perform rapid, goal-directed flexion and extension movements equally accurately in different parts of the elbow's workspace. In these experiments, movements of 10, 20 and 30 degrees in amplitude were tested using up to five different initial elbow angles. When performing flexions, subjects tended to overshoot targets when starting from extended positions, to undershoot targets when starting from more flexed positions, and to perform relatively accurate movements when starting from the centre of the workspace. Final position accuracy was more variable for extensions. When reliable differences existed for extensions, subjects tended to produce a pattern of results opposite to that of flexions: subjects overshot targets when starting from flexed positions and undershot targets when starting from more extended positions. A model of elbow movement based on the $ lambda$ version of the equilibrium-point hypothesis was used to assess the extent to which the pattern of errors obtained in the empirical studies could be reproduced by a control scheme that does not adjust commands in response to changing musculo-skeletal geometry, but rather uses one single invariant command throughout the workspace. The motivation for testing the invariant command notion was to explore the possibility that motion planning might be achieved without an explicit representation of musculo-skeletal geometry. Predicted patterns of final position errors across the workspace matched empirically obtained error patterns for flexions, but the model performed less well when predicting the pattern of errors observed for extension movements.

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