A system for protecting the legs of an occupant positioned in a seat of a vehicle from an explosive force originating under a floor of the vehicle. The system includes a movable bolster configured to move to contact the legs of the occupant and cause the feet of the occupant to move away from the floor of the vehicle. The system also includes a module positioned proximate the seat of the vehicle and including a movable rod linked to the bolster, wherein the module includes a gas generator configured to be activated to generate gas used to force the rod to move. The system also includes a controller that is configured to receive a signal from a vertical acceleration sensor and activate the gas generator when the signal from the sensor is indicative of a condition where the vertical acceleration of the vehicle exceeds a predetermined threshold.