Effects of load carriage on spinal motor control in schoolchildren

Backpack carriage is common in schoolchildren and has been shown to have significant effects on spinal muscles, head and trunk postures and spinal curvature. It was recently shown to affect spinal proprioception. However, the clinical implications of this effect are still unclear. Fractional Brownian method (fBM) has been proposed and applied to study the control of standing stability via the trajectory of centre of pressure (COP). Postural control strategies including closed- and open-loop control mechanisms as well as postural response time have been identified. The objectives of the current study are to explore the use of the fBM in quantifying spinal motor control in schoolchildren, and to investigate the effect of backpack carriage on spinal motor control in schoolchildren. Seven 15-years-old schoolboys were recruited. Children's spinal curvatures during upright quiet stance on a piece of foam with eye closed were measured with and without carrying a backpack equivalent to 15% of the children's body weight. The spinal curvatures of cervical, upper/lower thoacic, and upper/lower lumbar regions as well as pelvic tilt were measured using an electrogoniometric system. Based on the fBM, curvature-diffusion curves were plotted using the spinal curvature results. Similar to the postural control strategies observed in COP trajectory, two distinct patterns denoting open- and closed-loop spinal motor control strategies were identified from the curvature-diffusion plots. It was found that the spinal motor control was significantly affected by backpack carriage. The onset of the closed-loop control was delayed and the spinal curvature variability was increased during backpack carriage. The effects were more apparent at the cervical, upper thoracic and lower lumbar regions. As impaired motor control was observed in patients with low back pain, the findings of the current study provide insight on the possible association between load carriage and low back pain. Copyright © 2010 International Federation for Medical and Biological Engineering.