Effects of Sinusoidal Whole Body Vibration Frequency on Drivers' Muscle Responses 2015-01-1396
Low back pain has a higher prevalence among drivers who have long term history of vehicle operations. Vehicle vibration has been considered to contribute to the onset of low back pain. However, the fundamental mechanism that relates vibration to low back pain is still not clear. Little is known about the relationship between vibration exposure, the biomechanical response, and the physiological responses of the seated human. The aim of this study was to determine the vibration frequency that causes the increase of muscle activity that can lead to muscle fatigue and low back pain. This study investigated the effects of various vibration frequencies on the lumbar and thoracic paraspinal muscle responses among 11 seated volunteers exposed to sinusoidal whole body vibration varying from 4Hz to 30Hz at 0.4 g of acceleration. The accelerations of the seat and the pelvis were recorded during various frequency of vibrations. Muscle activity was measured using electromyography (EMG). The results demonstrated that peak muscle response from both upper and low back occurred at 5-6 Hz frequencies, which are also reported frequencies of peak transmissibility in vertical direction. The peak muscle response occurred at frequencies of peak transmissibility indicates that higher stretch amplitude of spinal muscle during resonant frequencies mainly induce the greater muscle activity. Those findings help us better understand the fundamental mechanism of driving discomfort and low back pain and avoid noxious vibration during NVH (noise-vibration-harshness) designs.