The biomechanics of lower abdominal steering-wheel loading

Twenty-five fully anesthetized swine were tested for biomechanical responses to lower abdominal steering-wheel loading. Supine subjects were impacted with the lower rim of a segmented steering wheel in a ventrodorsad direction at approximately the L-4 level of the lumbar spine. Peak force ranged from 0.13 to 8.56 kN, peak stroke from 16.1 to 123.8 mm, and peak velocity from 1.7 to 12.4 m/s. Mechanical response is presented in terms of force-deflection cross plots of force-time and displacement-time histories. Overall stiffness, normalized for equal stress-equal velocity scaling using a standard human cadaver mass, was found to be rate dependent and corridors are suggested. These findings indicate that the stiffness of the lower abdomen is less than upper abdominal stiffness and significantly lower than chest stiffness, although lower abdominal stiffness in living subjects is still slightly higher than it is in the lower abdomen of human cadavers. The maximum viscous response (VCmax) was a strong predictor of injury risk for the entire data set.