A lower body negative pressure (LBNP) device provides a controlled, measured orthostatic stress to the cardiovascular system. A person slides into the box so that the lower body up to the iliac crest. The lower body is then isolated from the room via the placement of a rubber seal similar to a Kayak skirt. Air is progressively removed from the chamber via a vacuum pump which increases the pressure from the inside to the outside of the lower limbs providing suction on the circulatory system and drawing blood away from the upper body. This simulates a loss of central blood volume which is commonly associated with upright posture or hemorrhage.