Fourteen normal healthy seated and restrained young adults were delivered rear-end impacts of four intensities of acceleration. The chair was delivered a regulated and controlled pneumatic blow using a 30 cm cylinder to cause an acceleration of 0.5, 0.9, 1.1 and 1.4g. The accelerated chair was stopped suddenly by impacting the stopper at the other end of the 2 m long friction reduced track. In one set of trials, subjects were informed about the impending impact and in the other they were blindfolded and provided with loud auditory input to eliminate cues of the impact. The accelerations of the chair, shoulder and head of the participating subjects were measured triaxially and compared between levels of acceleration and expectation. The multiple analyses of variance revealed that the peak acceleration was significantly affected by the gender (P less than 0.01), intensity of impact (P less than 0.001), and expectation (P less than 0,0001). The accelerations were significantly different in different axes (P less than 0.001). A significant two-way interaction between acceleration and expectation (P less than 0.03), and expectation and axes of acceleration (P less than 0.02) would imply that awareness of the impending impact services to significantly reduce the level of accelerations of head and neck. (Author/publisher).
Abstract