Acute effects of whole body vibration on directionality and reaction time latency of trunk muscles: the importance of rest and implications for spine stability.

Workplace exposure to whole body vibration (WBV) has been identified as one of the major physical risk factors encountered by the population. There are indications that, subsequent to a perturbation, impaired reflex response could allow for destabilization of the spine, possibly leading to injury. The purpose of this study was to investigate if WBV alters reflex response of trunk muscles and if the direction of perturbation (flexion or extension or lateral) and delay between exposure and perturbation influences the response. The results indicate that EMG latency was increased more in the vibration condition than in sitting without vibration. Significant effects with respect to directionality were observed in Erector Spinae muscles. The EMG latency reduced from the effect of perturbation after a 20s rest period. Even though the EMG latency did not fully return to its Pre-test state, the present results still show that recovery from the acute effects of WBV is possible with a rest period.