Background and aim: Since 1998, the effect of traction on the H- reflex has been investigated by Hiraoka and the other researchers. Some of them have been done on lower extremity and the other on the upper extremity. The effect of traction was assessed by H reflex amplitude. Different results have been achieved. The new method which has been used since 2000, the effect of cervical traction on the H reflex was carried out by measuring H reflex slope .In this experiment the effect of manual cervical traction has been studied on the H slope of the upper extremity. Now we have sought to extend this work by examining the effects of cervical traction with 3 kg force on the H slope of the lower extremity 

Materials and Methods: This study was administered to sixteen healthy men with a mean age 23.12 of years and SD=2.55. The parameters of H reflex were recorded before and after of cervical traction .All data were analyzed with SPSS (V: 11.5).    

Results: The results showed that, there were no significant differences between before and after the application of cervical traction in H reflex parameters, ratio of H max/M max amplitude and M slope. But H slope and ratio of H slope /M slope were increased significantly after the application of traction (P<0.001).

Conclusion: The present study showed that traction with 3 Kg force can increase motor neuron excitability of soleus muscle and this result is against the previous study. This could be due to the application of the new method (H slope), which is more precise.