|Title:||Biomechanical effects of castored chair height on the load of the lumbar spine during forward propulsion using feet|
Hong Kong Polytechnic University -- Dissertations
Jockey Club Rehabilitation Engineering Centre
|Pages:||xiv, 126 leaves : ill. ; 30 cm|
|Abstract:||Feet propulsion on a castored chair utilizing the frictional force between the feet and ground was become a very common activity while in a seated posture. The musculature of the lumbar region is of special interest because of the high incidence of painful disorder in this region, which may be associated with mechanical factors. Antagonistic trunk muscle coactivation is necessary to maintain the lumbar spine in a mechanically stable equilibrium. However, the advantage of lumbar muscles coactivation is offset by an increase in lumbar compressive forces. The intent of this investigation was to study the normalized surface electromyography (EMG) to facilitate the interpretation of lumbar muscles coactivation due to change of seat height (4 levels). Eleven subjects took part in this study. Muscles activities of left rectus abdominis, external oblique, erector spinae and latissimus dorsi were detected with telemetric surface electromyography technique. The raw EMG signals were normalized with the maximum voluntary isometric contraction. The trunk and knee segment motion was captured by Motion Analysis System. The EMG and the trunk motion data were synchronized for data analysis. Repeated measures analysis of variance was used to compare the mean value of each parameter at different seat heights. The results demonstrated that a lower seat height would cause higher lumbar muscle coactivation and higher seat height would cause higher lumbar muscle activities. Higher coactivation of lumbar muscle would induce additional compressive load on the lumbar spine and higher lumbar muscles activities would cause lumbar muscle fatigue. Forward feet propelling on castored chair is therefore not a desirable activity.|
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