There is a high incidence of TBI among warfighter occupants of vehicles targeted by underbody blasts but little is known about the unique forces involved or the pathophysiology. We hypothesize: Acceleration experienced during survivable underbody blasts produces dose-dependent, TBI. Underbody blast-induced acceleration combined with secondary head impact is also military relevant and can be modeled. Neurologic outcome following underbody blast-induced TBI can be improved by force-modifying vehicle hull designs. We will expand our underbody blast animal model of TBI to establish full dose-response relationships and to model the combination of acceleration plus head impact. This research will promote development of engineering- and biomedical-based neuroprotective interventions translatable to warfighter TBI.