Developed by Montana State University mechanical engineers, the Horseback Riding Trunk Support mounts in front of the rider and extends under the arms, thus supporting his/her entire trunk. The device, which doesn't hinder the rider's control over the horse, has two major components—(a) a polyethylene plastic saddle blanket permanently mounted to a steel sub-frame, and (b) an adjustable linkage to which a "chest cuff" is attached. The plastic blanket, sandwiched between the normal saddle blanket and the saddle, has its own cinching system for added stability; and the linkage allows adjustments to fit an individual's needs. The chest cuff easily detaches from the linkage to permit unhindered mounting and dismounting.