Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/2828
Title: The effects of backpack weights and positions on motor control of schoolchildren
Authors: Ou, Ziyang
Subjects: Hong Kong Polytechnic University -- Dissertations
Motor ability in children -- China -- Hong Kong -- Physiological aspects
Backpacking injuries -- China -- Hong Kong -- Physiological aspects
School children -- Health and hygiene -- China -- Hong Kong.
Issue Date: 2010
Publisher: The Hong Kong Polytechnic University
Abstract: Backpack is common load carried by schoolchildren throughout the world with weight ranged from 10% to 20% of children’s body weight. It was demonstrated that a backpack could adversely affect children’s physiological and functional performance. Moreover, spine curvature, spine repositioning consistency and stance stability were also affected during backpack carriage. However, the clinical implication of reduced spine repositioning consistency during load carriage is still not clearly understood. Fractional Brownian method has been proposed and applied to study postural control. Postural control scheme for closed/open-loop control could be identified by plotting a stabilogram-diffusion plot based on the fractional Brownian method. In this study, similar method was adopted to study the motor control of children’s spine and the effects of different backpack weights and positions on the motor control of spine and postural balance were studied. Eighty-four children aged 11 or 15 years old were recruited. They were randomly assigned to one of the 3 experimental groups for carrying different backpack weights (10%, 15% and 20% body weight (BW)) with matched gender and age. The children were requested to carry a backpack at six different conditions (i.e. anterior or posterior with the backpack centre of gravity located at T7, T12 or L3 level), together with an unloaded condition. The changes of centre of pressure (COP) motion and spinal curvature at different experimental conditions were measured using a force platform and a self-developed electrogoniometric system. It was shown that similar to postural control schemes identified for COP control, two control mechanisms were identified for spinal postural control, namely open-and closed-loop control. The spinal control for 11-year-old children was found to be poorer than that of 15-year-old children. The postural balance control was found to be significantly affected by backpack carriage with increased speed, range and randomness of COP motion. The effects on balance control during load carriage were found to be more apparent with the backpack centre of gravity positioned at high level. The findings also showed that control of spine curvature variability was significantly affected by load carriage with apparent difference between anterior and posterior carriages. There was a delay in onset of closed-loop control as well as an increase in curvature variability at the upper and lower lumbar regions during posterior carriage. Spinal motor control was relatively less affected during anterior carriage. For both anterior and posterior carriage, the effects on spinal motor control were significantly higher when the load was positioned at high level (i.e. T7) in comparison to low levels. Relatively, the spinal motor control was less affected when the load CG was positioned at T12. Thus, an anteriorly carried load with CG located at T12 was shown to have minimum effect on spinal motor control.
Description: xx, 250 p. : ill. ; 30 cm.
PolyU Library Call No.: [THS] LG51 .H577M HTI 2010 Ou
Rights: All rights reserved.
Type: Thesis
URI: http://hdl.handle.net/10397/2828
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