Abstract
The purpose of this study was to investigate the effects of cervical traction on the soleus H reflex amplitude. Young healthy men were recruited as the subjects. In experiment 1, cervical traction under three conditions, i. e. at an intensity of 3 kgf, 6 kgf or 9 kgf was applied to the subjects in the experimental group for a duration of 1 minute in the second minute of each trial. In experiment 2, cervical traction at an intensity of 3 kgf for a duration of 1 minute, 2 minutes, or 3 minutes was applied to the subjects in the experimental group. Cervical traction was not applied to the subjects in the control group. The soleus H reflex amplitude was measured before, during, and after cervical traction.
The H reflex amplitudes under the 9kgf condition were largest and positive for every block, whereas those under the 3 kgf condition were smallest among the three experimental conditions employed. Significantly smaller H reflex amplitude compared to that in the control was observed under the 3 kgf condition.
In experiment 2, the H reflex amplitudes under every experimental condition employed were smaller than that in the control. However, the differences in degree of depression of the soleus H reflex amplitudes among the three duration conditions were not significant.
This study shows that cervical traction at an intensity of 3kgf depresses the gain of the soleus H reflex pathway. The cause of this depression may be an “after-effect” or flexor reflex afferents. A difference in the duration of cervical traction didn't result in any difference in the soleus H reflex amplitude.
