Biomechanical effects of load carriage on spine curvature and proprioception

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Biomechanical effects of load carriage on spine curvature and proprioception


Author: Wang, Xinguang Chris
Title: Biomechanical effects of load carriage on spine curvature and proprioception
Degree: M.Phil.
Year: 2008
Subject: Hong Kong Polytechnic University -- Dissertations.
Backache -- Diagnosis.
Backpacking -- Physiological aspects.
School children -- China -- Hong Kong -- Health and hygiene.
Spine -- Wounds and injuries -- Diagnosis.
Department: Dept. of Health Technology and Informatics
Pages: xiii, 136 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record:
Abstract: Low back pain is a common problem affecting people. At least 90% of school children were reported to use backpacks in the developed countries. The excessive loading due to daily backpack carriage was reported to increase the stress across the joint and be associated with increased risk of back pain. However, the quantitative studies rebated to the effects of different backpack weights and carrying methods on spine curvature and proprioception are still limited. In this study, 63 normal subjects with age between 11 and 15 years old were recruited. A backpack with a self-designed inside frame was applied to the subjects. The weight of backpack was proportional to the subject's body weight (BW). Each subject was asked to repeat upright stance for 6 times without backpack or carrying a backpack (10%BW, 15%BW or 20%BW) with different backpack centre of gravity (CG) locations (T7, T12 and L3) and carrying methods (anterior and posterior). The spine curvature and repositioning error were determined using a self-developed electrogoniometric system. Statistical analysis was performed to investigate the effects of backpack weight, backpack CG location and carrying method on the spine curvature and repositioning ability. Both anterior and posterior carriages were found to induce different postural responses. For the posterior carriage, the cervical extension and lumbar flexion were shown to respond to the posterior load. The pelvic anterior tilt was triggered when the backpack weight was heavier than 15%BW. A turning region was also observed at the thoracic region in posterior carriage. A shift of increased repositioning error up the lumbar spine with increased backpack load was demonstrated in posterior carriage. For the anterior carriage, the upper thoracic kyphosis increased significantly in response to the anterior load. The pelvic posterior tilt was triggered with the increase of load from 10%BW to 15%BW. Low CG location (T12 and L3) was shown to induce less postural changes in 10%BW and 15%BW carriages when comparing to the high CG location (T7). In 15%BW carriages, it was also found that the spine levels above the backpack CG location extended to counterbalance the front load. The 20%BW carriages may result in a different strategy in balancing the front load. In this study, the electrogoniometric system was shown to be a feasible method for spine curvature quantification and proprioception assessment. Different patterns of spine curvature and repositioning error were demonstrated to respond to the anterior and posterior carriages. The effects of backpack CG location were not obvious for posterior carriage. Anterior carrying method seems to have no apparent benefit to the spine when comparing to posterior load carriage. The lower CG location may be better when the load has to be carried anteriorly. The poor repositioning ability induced by both anterior and posterior carriages at different spine levels may result in a high demand to the spine. A deeper understanding of the implication of the reduction in repositioning ability may provide insight whether this is related to the increased back pain observed in adolescents.

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