The effect of fatigue on postural stability during repetitive trunk bending motion in healthy and chronic non-specific low back pain subjects

Document Type : Original Articles


1 Assistant Professor, Department of Ergonomics, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran

2 Professor, Department of Mechanical Engineering, Sharif University of Technology, Tehran, Iran

3 Assistant Professor, Biomechanics Lab, Rehabilitation Research Center, Department of Rehabilitation Basic Sciences, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran



Introduction: This study was a quasi-experimental, case-control design to investigate the effect of fatigue on postural stability during repetitive trunk bending motion in subjects with chronic low back pain and healthy adults. Materials and Methods: Fourteen healthy volunteers and thirteen subjects with low back pain participated in this research. They performed repeated trunk bending motion in mid sagittal plane until exhaustion. All data were divided into three parts then first and third parts were compared together. Some variables like standard deviation of amplitude, standard deviation of velocity in anterior-posterior and medial-lateral directions mean total velocity and path length were calculated. Paired and Independent T-test were used to explore the pre/post fatigue and the between groups difference. Results: The results showed that fatigue had a significant effect on the mean total velocity and amplitude standard deviation in anterior-posterior direction in healthy subjects. There was no effect in low back pain participants. Also, no difference was observed between two groups at the beginning of the test in postural stability. Conclusion: Results suggested that the Postural control system of chronic low back pain patients is distinguishable from the healthy adults’ one, just in an induced perturbation condition. Also healthy subjects showed the different strategies in response to fatigue compared to low back pain subjects. Keywords: Postural balance, Fatigue, Low back pain