Effects of back extensor and hip abductor fatigue on dynamic postural stability in patients with nonspecific chronic low back pain: A case-control study

Introduction Patients with nonspecific chronic low back pain (NSCLBP) complain of pain and fatigue during functional activities. Poor back muscle endurance has been associated with recurrent pain and long-term disability. However, the relationship between proximal muscle fatigue and postural stability is not well understood. Purpose To investigate the effects of lumbar extensor and hip abductor fatigue on postural stability in NSCLBPs. Methods To induce isolated fatigue, participants (24 LBPs, 24 controls) were asked to perform multiple back extension and hip abduction in the separate sessions until the muscle force reached 60% of pre-fatigued force. The overall (OSI), anteroposterior (APSI), and mediolateral (MLSI) stability indices were measured during single-leg stance using the Biodex dynamic platform. Results The results revealed higher postural instability (APSI and OSI) following fatiguing lumbar extensor and hip abductor muscles (greater effect size for APSI than OSI) in LBPs than controls. Furthermore, significant and inverse relationships were found between the level of physical activity, pain, and post-fatigue postural instability (OSI) in NSCLBPs. Conclusion Fatigue of proximal muscles could differentiate postural stability primarily in the sagittal plane between NSCLBPs and controls. Therefore, reducing the fatigability of these muscles by endurance training in addition to balance training may improve physical activity.