Objective. The aim of this study was to examine whether differences existed in spinal kinematics and trunk muscle activity in cyclists with and without non-specific chronic low back pain (NSCLBP).Design. Two independent-group comparison study. Background. Cyclists are known to be vulnerable to low back pain. However, the aetiology of this problem has not been adequately researched. Causative factors are thought to be prolonged forward flexion, flexion-relaxation of the erector spinae, mechanical creep and generation of high mechanical loads while being in a flexed and rotated position. Methods. Nine asymptomatic cyclists and nine cyclists with NSCLBP with a flexion pattern disorder primarily related to cycling were tested. Spinal kinematics were measured by an electromagnetic tracking system and EMG was recorded bilaterally from selected trunk muscles. Data was collected every five minutes until back pain occurred or general discomfort prevented further cycling. Results. Cyclists in the pain group showed increased lower lumbar flexion and rotation with associated loss of co-contraction of the lumbar multifidus. This muscle is known to be a key stabiliser of the lumbar spine. Conclusions. The findings suggest altered motor control and kinematics of the lower lumbar spine are associated with the development of low back pain in cyclists. Relevance. Low back injuries in cyclists are common, however, there is little known about the aetiology of injury. Clinicians will be better equipped to rehabilitate these injuries with an increased knowledge of the mechanisms of pain in the lumbar spine.