Military vehicle underbody blast is the cause of many serious injuries in theatre today. The purpose of this research was to determine the loading conditions relevant to underbody blast which would produce characteristic lower extremity and pelvis injuries. In addition to better understanding the response of the human to high rate vertical loading, this test series also aimed to supplement the available information on the response of the Hybrid‐III under such loading conditions. Five full body matched pair post mortem human specimen (PMHS) and Hybrid‐III anthropometric test device (ATD) tests were completed using the University of Virginia’s ODYSSEY simulated blast rig under a range of loading conditions. Seat pan loading accelerations ranged from 291 to 738 g’s over three milliseconds and foot pan accelerations from 234 to 615 g’s over three milliseconds. Post‐test CT scans and necropsies were performed to determine any injuries, and revealed a combination of pelvic, lumbar, thoracic, and lower extremity injuries. This research demonstrates the inaccuracy of the Hybrid‐III under high rate vertical loads as well as preliminarily suggest the vertical injury threshold for the pelvis exists around 300g’s of acceleration and 6.5 m/s peak velocity in 5 ms, while the threshold for the lower extremities lies in excess of 600 g’s of acceleration and 10 m/s peak velocity in 4.5 ms.