POSTURAL STABILITY AND SPINAL MOVEMENT IN CHRONIC LOW BACK PAIN

Movement of different body segments is an essential component for the control of postural stability. Notably, balance impairment has been reported in individuals with chronic low back pain. Various impairments that are likely to affect postural control have been reported in this population, including proprioceptive deficits and altered control of movement at the lumbopelvic region. Although little is known about how movement of the lumbar spine contributes to postural control, spinal movement is likely to be part of the movement strategy when the multisegmental nature of the human body configuration is taken into consideration. The overall objective of this thesis was to investigate the changes in postural stability in individuals with chronic LBP, and the association with altered movement control at the lumbar spine. The control of postural stability was examined with different postural challenges while standing on either a flat surface or a short base. A short base was used to force the subjects to use a “hip strategy”; movement at the lumbopelvic region for postural correction. Kinematics of different body segments including the lumbar spine and hip were recorded to study the movement of the lumbopelvic region. In addition, ground reaction force data were collected with a force platform system to examine postural adjustments during various postural tasks. The studies showed that people with chronic low back pain have difficulty maintaining stance, with increased risk of overbalancing when standing on a short base without any perturbation. Altered motion of the lumbar spine was evident during both expected and unexpected postural perturbations, which indicated impairment of both anticipatory and feedback control of lumbar motion in individuals with chronic low back pain. In addition, subjects took longer to regain postural stability and made more postural adjustments during the recovery period after expected and unexpected perturbations. Together, the studies suggested significant contribution of changes in lumbar motion to postural impairment in people with chronic low back pain. In summary, these findings provide further evidence that spinal movement plays a critical role in the maintenance of postural stability, and altered control of movement affects the quality of postural control in individuals with chronic low back pain