IntroductionRecent studies of whole body vibration in seated postures have suggested that the neuromotor system may play a role in the etiology of low back disorders [1][2][3][4] . A number of researchers have modeled whole body vibration transmission to the low back, spine and head 5 . However, no model to our knowledge has examined the transmission of mechanical vibration to muscle shortening/lengthening, the neuromotor system and reflex muscle activation. In addition, only a few studies have examined biodynamic vibration transmission in the fore-aft (anterior-posterior) direction. In this work, transmission of fore-aft vibration to the spine rotation and erector spinae muscle activation was assessed and a model of the motion was created.

Low back pain is one of the most costly and common musculoskeletal disorders, affecting up to 80% of the adults in their lifetime [1]. Whole body vibration (WBV) has been found to be a major risk factor in the etiology of low back pain with WBV increasing low back disorder risk from 1.2 to 39.5 fold depending on the occupational exposure duration and magnitude [2–3]. Recent research has demonstrated that exposure to sinusoidal whole body vibration of 5 Hz leads to increased propriceptive errors and delayed neuromotor response to external perturbation [4]. These results suggest a potential mechanism for low back injuries, namely that vibration may alter neuromotor control leading to poor stabilization and control of low back motion, increasing the risk of injury. However, the methods used to assess these changes in proprioception are static measures, require a good deal of equipment and setup time, and have a high variance, particularly with removal of electrodes and sensors, that make them impractical for the industrial setting. In addition, previous studies have only examined the effect of pure sinusoidal vibration exposure rather than the mixture of frequencies seen in occupational settings. Therefore, the goal of this project was to develop a dynamic measure of lumbar sensory accuracy and neuromotor control that could be used easily in the workplace and to examine the effects of WBV vibration on the measure using an occupationally-relevant vibration exposure.