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The tolerance to abrupt linear deceleration (-Gx) and impact trauma patterns resulting from the use of the Air Force shoulder harness-lap belt restraint were investigated. Eighty-nine deceleration tests were performed with 37 adult male baboons. Peak sled decelerations ranged from 6.5-134 g. The stopping distance varied from 0.5-3.5 ft at 6 in increments. LD50s were calculated to be 102, 103, and 98 g for the 0.5, 2.0, and 3.5 ft stopping distances, respectively. Since the deceleration pulses were similar, the results imply that for the exposure range of these tests, impact lethality is dependent upon magnitude of peak sled deceleration, irrespective of the pulse duration, sled velocity, or stopping distance. At all stopping distances, the primary cause of death was lower brainstem or cervical spinal cord trauma. The pelvic, abdominal, and thoracic injury patterns were significantly different at the various stopping distances.

The tolerance to abrupt linear deceleration (- Gx) and the subject response to a lap belt restraint system were investigated. Nineteen adult male baboons comprised the test pool. The effects of impacts of 8.6-40 g were studied, with nonsurvivability used as the index of tolerance. The results indicated that the tolerance to impact (LD50) approximated a 32 g sled deceleration. Lethality was presumed attributable to the secondary impact as the head contacted the floor of the sled. Predominant lethal injuries included avulsion of the atlanto-occipital articulation and dislocation fractures of the cervical vertebrae with resulting transection of the spinal cord. Excellent linear correlations were established between peak lap belt and seat pan forces versus maximum sled deceleration. Likewise, a linear relationship was found between peak head angular accelerations and maximum sled deceleration.