Modulation of the Flexor Carpi Radialis H Reflex Induced by Cervical Traction.

Abstract

The purpose of this study was to investigate the effects of cervical traction on flexor carpi radialis H reflex amplitude in ten healthy men who were held in a fixed supine position. Cervical traction at intensities of 3, 6, and 9 kgf was applied for one minute and the H reflexes were evoked before, during and after the application of traction. At each intensity tested, cervical traction showed the tendency of facilitating the H reflex, and, especially, the H reflex amplitude during and after the application of cervical traction at an intensity of 3 kgf was significantly greater than that under the condition where no traction was applied. Cervical traction of greater intensity tended to have a stronger facilitatory effect on H reflex amplitude. These results were opposite to the findings in a previous study concerning the soleus H reflex performed by the same experimental procedure. These results suggest that a facilitatory mechanism and an inhibitory mechanism interact and the sum of these mechanisms modulates the gain of the FCR H reflex pathway. Flexor reflex afferents may play a role in the facilitatory mechanism.