Abstract OBJECTIVE: To compare the differences in paraspinal muscle electromyographic indices between patients with ankylosing spondylitis (AS) and healthy volunteers and to investigate the value of electromyography in assisting the evaluation of AS treatment outcomes. METHODS: Electromyography was applied to measure the electromyographic indices of paraspinal muscles at the L1 and L4 levels in 32 patients with ankylosing spondylitis, and the average time frame and wave amplitude of 20 motor unit potentials of the muscles during small force contractions were recorded. Finger-ground distance, occipital wall distance, Schober test, pain and fatigue scores were also measured, and 32 healthy volunteers served as controls. RESULTS: The paraspinal muscle EMG indexes were significantly abnormal in patients with ankylosing spondylitis compared with the control group (P