| Abstract |
This work studied in vivo, the effects of common loading environments on the mechanical response of the seated human. The eventual goal of this work is to evaluate and control the occupational health hazard of low back pain, a musculoskeletal injury, by establishing an 'envelope' of loading conditions which should not be exceeded if the spine is to avoid mechanical damage. Proceeding from prior in vitro findings of short-column buckling in the lumbar spine following vibration exposure, this proposal evaluated how the supporting trunk musculature responded to an unexpected load application after a 40-minute vibration or static load intervention (seated vertical vibration, seated lateral vibration, seated lateral and vertical vibration or sitting still (as a control)). This simulated the sudden and unexpected shift of an object in the hands of the car or truck driver who has driven for 40 minutes at an exposure level consistent with the 8-hour, Fatigue, Decreased Proficiency level of the ISO 2631 (1985) guideline on human exposure to whole-body vibration. Normal walking (as a break) for five minutes, prior to an unexpected load application, was also tested to determine if it would serve as a reasonable control measure. This would allow lumbar discs to return, via creep behavior, to the upright posture orientation where the facets are more firmly engaged. |
