Airline travel, particularly over extended distances, can be very taxing on the human body. Passengers may have to stay seated on board an aircraft for fifteen to eighteen hours on some long distance international flights. Staying seated for hours at a time has certain health risks. The most serious is the development of blood clots or thrombosis, which can form in the veins or arteries of the lower extremities and result from being seated for long periods. Such conditions are extremely painful and if not treated immediately can lead to tissue damage and necrosis (tissue death) in the legs or other parts of the body. Parts of the blood clot may break off and travel to other parts of the body and possibly leading to pulmonary embolism or stroke, which are life threatening conditions. Such conditions are thought to be associated with excessive pressure on the back of the thighs and buttocks for extended periods of time. Similar problems are faced by bus passengers.
Also, airline or bus passenger seats or seats in other areas such as waiting rooms may not be very comfortable, with the result that passengers or persons may become impatient, irritable, or frustrated and not be able to stay seated for the required duration of time. Accordingly, the level of comfort provided by many types of seats commonly used by the public has not been entirely satisfactory.