The Effect of Fatigue and Instability on Postural Control Parameters in Standing Posture in Healthy Adults and Patients with Chronic Low Back Pain

This study aims at analyzing the effect of fatigue and instability on postural control parameters in both healthy people and patients with the chronic nonspecific low-back pain. In this non-experimental case-control study, oscillations of center of pressure were statistically analyzed in 16 healthy people and 15 patients with the chronic nonspecific low back pain. The analysis was conducted through two stages: before and after fatigue and under both stable and unstable surfaces. Under the pre-fatigue, stable condition, there was not any difference between the two groups. Both fatigue and unstable surface changed our variables (sway area, range, velocity, frequency and total power of the signal). All the changes in variables were significant in the low-back pain group; while changes in the healthy group only covered the time-domain variables. The effect of instability was higher than that of fatigue. The postural control system for patients with low-back pain before fatigue and under stable condition, revealed sufficient competence to provide postural stability and its function cannot be differentiated from that in healthy people. Meanwhile, different mechanisms were used by these patients to confront stability challenging factors and further neural activity was required to counteract such factors.