Change of paraspinal muscle spindle resting discharge evoked by mechanical vibration.

Mechanical vibration is experienced by people in some occupations. Low back pain has been linked to whole body vibration. The resting discharge of 26 paraspinal muscle spindles of anesthetized cats were recorded at L6 dorsal roots before, during and after the application of mechanical vibration at L6 spinous process. Paired student's t-test was used to compare the resting discharge before and after mechanical vibration. After vibration, the mean instantaneous frequency of the resting discharge for most of the muscle spindles (81%) decreased significantly (P<0.01). The average normalized decrease was -9.4%. The coefficient of variation for instantaneous frequency for most muscle spindles (62%) increased significantly (P<0.01). The average normalized increase was 60.5%. The results shed light on changes in proprioceptive input from the low back that can be induced by mechanical vibration.