Objective To compare the effects of nonsurgical spinal decompression system (SDS) cervical traction and common cervical traction using surface electromyography (sEMG).Methods Twenty-two volunteers' sEMG signals were recorded before,during and after two modes of cervical traction:the conventional traction in sitting and SDS traction in supine.The interval between the two modes of traction was no shorter than 24 hours.The mean and peak amplitudes of their sEMG signals were observed before,during and after traction.The sEMG signals of the posterior cervical muscle while sitting or lying were compared at different stages of the traction.Results There was no statistically significant difference in sEMG signals between the subjects' right and left posterior cervical muscles.The sEMG signals decreased significantly during both traction trials.With common cervical traction the mean and peak amplitudes of the left posterior cervical muscle pre-and post-traction were higher than during traction,and the same as that of the right posterior cervical muscle.In the SDS trials the sEMG signals during traction and post-traction were significantly lower than those pre-traction.After traction the sEMG signals while sitting (common cervical traction) were significantly higher than those post-traction while lying (SDS cervical traction),and the sEMG signals post-traction while either lying or sitting were stronger than during traction while lying.The post-traction signals in sitting were stronger than those in lying.Conclusions Both nonsurgical SDS and common cervical traction can relax the posterior cervical muscles.The effect of nonsurgical SDS was better than that of common cervical traction.