Though people sit on the floor also, a high platform for sitting purpose is usually designated as a seat. Normally, seats mean chair type seating with and without arm rest and stool types of seat without backrests. Depending on the various contexual requirements there are varieties of designs and some new ones are also being developed. Whatever the consideration, aesthethics., etc., the primary consideration should be comfort, so that, people can sit on the seat for a long time without feeling any physical as well as physiological discomfort. The general problems encountered in seats not meeting the body as shown.
To arrive at a comfortable design for seats, the human body dimensions, and the static anthropometry of the user should be considered first, followed by dynamic dimensional variations along with task contextual behavioural demands. The selection of anthropometric details and the relevant design features would depend on these requirements. Generally, seating is directly to other furniture, e.g. tables, counters, desk, a variety of work surface and spaces. Seats for general purposes included common chairs
used in homes, offices, etc. Under the category of special seats, low seating arrangements range from sofas to car seats and train compartment seats.
Everyone would not be comfortable on a seat if a proper back rest, full thigh-buttock support, arm rest and proper foot holding are not provided. Unlike the common seats, for certain tasks, like typing, drafting, etc., where forward bending is required, the concept of a 15 degree forward inclined seat has been developed as an alternative for use in sedentary work, e.g. Balans chair concept. Noe back rest is required as the hip angle is below 90 degrees. The forward inclined body is supported by a knee support. Though it has several advantages towards supporting the normal body posture adopted during some sedentary work, further exploration is awaited and possible beneficial effects are being tested.
A combination of these two concepts of forward inclined and conventional horizontal or backward inclined seats using proper adjustable tilting mechanisms of forward and back inclinations, with appropriate back rests may be tried out for general purposes. Here, the general human dimensions related to specific parts of the seating device would be discussed instead of taking examples of every type of seat of various contextual requirements.
The commonly used seats have the following parts, a) Seat surface, b) Seat stand for seat height, c) back rest d) arm rests and e)cushioning. Other seat related considerations are, a) Leg room, b) foot rest and, c) clearances.