When the employee can alternate sitting with other body positions, sitting at work is not a risk for injury or discomfort.
For those who have no choice and must sit for long periods, the situation is different. Although sitting involves less muscular effort than such physically demanding jobs as gardening or floor mopping, it still causes fatigue. Sitting requires the muscles to hold the trunk, neck and shoulders in a fixed position. A fixed working position squeezes the blood vessels in the muscles reducing the blood supply to the working muscles just when they need it the most. An insufficient blood supply accelerates fatigue and makes the muscles prone to injury.
Sedentary employees may also face a gradual deterioration in health (if they do not exercise or do not lead a physically active life). Prolonged sitting drops the employee's physical activity to the lower limit needed for healthy-body functioning. The most common health problems that employees suffer are disorders in blood circulation and injuries affecting their ability to move.