Postural stability and trunk muscle responses to the static and perturbed balance tasks in individuals with and without symptomatic degenerative lumbar disease.

BACKGROUND: Degenerative lumbar diseases (DLDs) are characterized by motor functional deficits and postural instability. In this study, we investigated the differences in the trunk muscle responses to postural control between the presurgical DLD patients and healthy individuals while performing the static and perturbed balance tasks.

METHODS: Thirty-five DLD patients (aged 61.1 ± 8.0 years) and thirty-five asymptomatic controls (aged 62.9 ± 3.7 years) participated in this study. All participants stood on a force plate and performed the quiet standing (QS) and in situ weight-lifting (WL) tasks. The participants' performance in the QS task was tested under the eyes-open, eyes-closed, wide-base, and narrow-base conditions. Center of pressure (CoP) movements and electromyography of the erector spinae (ES) were recorded. The Mann-Whitney U test was applied for statistical analysis.

RESULTS: The DLD group showed a significantly greater CoP movements and muscle activations during the QS task. Nevertheless, smaller CoP movements were noted during the WL task in the DLD group. Under the eyes-closed and narrow-base conditions, the DLD group showed even higher muscle activations and CoP movements.

SIGNIFICANCE: The DLD patients demonstrated a poor postural control ability and tended to rely on the visual feedback and wide-base standing posture. A rigid and restricted posture was also adopted during the perturbed WL task. A high level of ES activation was required to maintain their postural steadiness. This study reveals an aberrant pattern of postural control and trunk muscle activations in symptomatic DLD patients which potentially contributes to the development of beneficial rehabilitation programs.