Axial compressive spine loading may occur through impact with the pelvis in multiple scenarios. A previous study demonstrated out of 122 CIREN cases, 52 occupants had fractures at the T12 or L1 vertebrae. The literature documenting fracture levels from military events include reports that indicate ejection seat events produced more trauma at the lower thoracic levels, helicopter crashes produced more fractures at the thoracolumbar junction, and underbody blast events produced more trauma at the mid to lower lumbar levels. The goals of the present study were to understand the effect of pulse differences on injury outcome and understand the differences between pelvis and spine trauma with an input acceleration to the seat bottom in the inferior-to-superior direction. Five PMHS were run in 15 tests on a Seattle Safety systems acceleration thrust sled. Additional Hybrid-III fiftieth male dummy tests were also conducted. Triangular pulses were used initially and varied from 1 G/msec, to 5 G/msec, to 10 G/msec and pulse durations of 40, 20, and 10 msec. In latter tests a sigmoid-shaped pulse with pulse durations on the order of 50 to 60 msec were used. The triangular pulses at 5 and 10 G/msec produced pelvic fractures but no spine fractures. The sigmoid-shaped pulse with 60 msec duration produced no pelvic fractures but did produce an L1 burst fracture. The Hybrid-III with the straight lumbar spine demonstrated higher Z-axis lumbar spine loads in the matched-pair test condition that induced an L1 burst fracture than the dummy with a curved spine.