Sitting is a basic human action and resting position. The body weight is supported primarily by the buttocks in contact with the ground or a horizontal object such as a chair seat. The torso is more or less upright. Sitting for much of the day may pose significant health risks, and people who sit regularly for prolonged periods have higher mortality rates than those who do not.
The form of kneeling where the thighs are near horizontal and the buttocks sit back on the heels, for example as in Seiza and Vajrasana (yoga), is also often interpreted as sitting.
PrevalenceThe British Chiropractic Association said in 2006 that 32% of the British population spent more than ten hours per day sitting down.
On the floorThe most common ways of sitting on the floor involve bending the knees. One can also sit with the legs unbent, using something solid as support for the back or leaning on one's arms. Sitting with bent legs can be done with the legs mostly parallel or by crossing them over each other.
A common cross-legged position is with the lower part of both legs folded towards the body, crossing each other at the ankle or calf, with both ankles on the floor, sometimes with the feet tucked under the knees or thighs. The position is known in several European languages as tailor style, from the traditional working posture of tailors; compare tailor's bunion. It is also named after various plains-dwelling nomads: in American English Indian style, in many European languages "Turkish style", and in Japanese . In yoga it is known as sukhasana.
On a raised seat
Most raised surfaces at the appropriate height can be used as seats for humans, whether they are made for the purpose, such as chairs, stools and benches, or not. While the buttocks are nearly always rested on the raised surface, there are many differences in how one can hold one's legs and back.
There are two major styles of sitting on a raised surface. The first has one or two of the legs in front of the sitting person; in the second, sitting astride something, the legs incline outwards on either side of the body.
The feet can rest on the floor or on a footrest, which can keep them vertical, horizontal, or at an angle in between. They can also dangle if the seat is sufficiently high. Legs can be kept right to the front of the body, spread apart, or one crossed over the other.
The upper body can be held upright, recline to either side or backward, or one can lean forward.
Yoga, traditions and spiritualityThere are many seated positions in various traditions and rituals. Four examples are:
In various mythologies and folk magic, sitting is a magical act that connects the person who sits with other persons, states or places.
Kneeling chairsThe kneeling chair (often just referred to as "ergonomic chair") was designed to encourage better posture than the conventional chair. To sit in a kneeling chair, one rests one's buttocks on the upper sloping pad and rests the front of the lower legs atop the lower pad, i.e., the human position as both sitting and kneeling at the same time.
In 1700, De Morbis Artificum Diatriba, listed sitting in odd postures as a cause of diseases in “chair-workers”. Current studies indicate there is a significantly higher mortality rate among people who regularly sit for prolonged periods, and the risk is not negated by regular exercise, though it is lowered. The causes of mortality and morbidity include heart disease, obesity, type 2 diabetes and cancer, specifically, breast, endometrial, colorectal, lung, and epithelial ovarian cancer. The link between heart disease and diabetes mortality and sitting is well-established, but the risk of cancer mortality is unclear. Sedentary time is also associated with an increased risk of depression in children and adolescents. A correlation between occupational sitting specifically and higher body mass index has been demonstrated, but causality has not yet been established. There are several hypotheses explaining why sitting is a health risk. These include changes in cardiac output, vitamin D, inflammation, sex hormone activity, lipoprotein lipase activity, and GLUT4 activity due to long periods of muscular unloading, among others.
Sitting may occupy up to half of an adult's workday in developed countries. Workplace programs to reduce sitting vary in method. They include sit-stand desks, counseling, workplace policy changes, walking/standing meetings, treadmill desks, breaks, therapy ball chairs, and stepping devices. Results of these programs are mixed, but there is moderate evidence to show that changes to chairs (adjusting the biomechanics of the chair or using different types of chairs) can effectively reduce musculoskeletal symptoms in workers who sit for most of their day.
Public health programs typically focus on increasing physical activity rather than reducing sitting time. One major target for these public health programs is sitting in the workplace. For example, WHO Europe recommended in September 2015 the provision of adjustable desks in the workplace. In general, there is conflicting evidence regarding the precise risks of sitting for long periods. A 2018 Cochrane review found low-quality evidence that providing employees with a standing desk option may reduce the length of time some people sit at work in the first year. This reduction in sitting may decrease with time, and there is no evidence that standing desks are effective in the long term. In addition, a 2018 British Journal of Medicine systematic review concluded that interventions aimed at reducing sitting outside of work were only modestly effective. It is not clear how standing desks compare to other work-place interventions to reduce the length of time employees are sitting during the work day.