Few things are more natural than standing or sitting. They pose no particular
health hazard in and of themselves. But at work, posture is dictated by the
work area and by the various tasks a worker is called upon to perform.
Aside from sore feet, standing jobs such as sales, assembly lines and machine
operating, that involve being on one's feet for prolonged periods can cause
swelled legs, varicose veins, general muscular fatigue, low back pain,
stiffness in the neck and shoulders, and other health problems.
Mechanization and automation has increased the number of sitting jobs - from
office workers to trades people operating machinery. In fact, reports of
varicose veins, stiff necks, and numbness in the legs are more common among
seated employees than among those doing heavier tasks.
AplusA-online.de - Source: Canadian Centre for Occupational Health and Safety (CCOHS