The co-contraction features of the lumbar muscle in patients with and without low back pain during multi-movements

Despite the important role played by muscle co-contraction in stabilizing and stiffening the spine during daily activities, the effects of multi-movement models on the lumbar co-contraction are yet to be explored. This study explores the co-contraction features of lumbar muscle in subjects with and without low back pain while they perform four different movements namely forward, backward, left flexion and right flexion lumbar actions. Surface electromyography (EMG) signals of three paired lumbar muscles were measured from a total number of 60 subjects while they performed specified movement models. Co-contraction ratio (CCR), defined as ratio of normalized integration of antagonist EMG activities to the total muscle activities, were accessed, and questionnaires about pain intensity were collected with visual analogue scale (VAS). The results showed that the CCR of LBP at forward (p = 0.007) and right flexion (p = 0.011) models was significantly greater than that of healthy controls, respectively. Also, CCR was significantly different among forward, backward, left flexion and right flexion models (p<;0.05). Finally, co-contraction patterns from LBP subjects reveal disordered neuromuscular control in regulating the stiffness of lumbar spine.