The effect of external load on postural stability during quit standing in healthy and non-specific low back pain subjects

The purpose of this study was to identify the effects of external loads on balance control during upright stance in Chronic Low Back Pain (CLBP) patients and healthy adults. This study was a qausi-experimental design. External loads were applied to 23 young، healthy participants and 21 low back pain subjects، and effects on balance control were characterized by Center-of-Pressure (COP) based measures. Center COP data were used to calculate standard deviation of amplitude، standard deviation of velocity in anterior-posterior and medial-lateral directions، mean total velocity and phase plane parameters. We used two way ANOVA to explore the pre/post applying external load and the between groups difference. The results showed that applying external load had a significant main effect on the standard deviation of amplitude in anterior-posterior and medio-lateral direction and parameters. There was no interaction of load and group in this study. Also there was no difference between two groups at the beginning of the test. These data show that wearing 10 kg of external weight in a waistcoat increases the postural sway of subjects، which may in turn increase the likelihood of falls and injury.