Cornell University Ergonomics Web
The Perils of Sitting
Sitting for more than 1 hour has been shown to induce biochemical changes in lipoprotein lipase activity (an enzyme involved in fat metabolism) and in glucose metabolism that leads to the deposit of fats in adipose tissue rather than these being metabolized by muscle, and extensive sitting also relates to heart disease risks, so people are advocating standing to work because this use more muscle activity (burns about 20% more calories). These changes happen in both fit people who regularly aerobically work out and also unfit and obese people, and regular exercise doesn’t necessarily address this. Recent studies have indicated a possible increase in the risks of coronary heart disease and kidney disease from excessive sitting. However, the data are correlational and what is unclear from these studies is whether it is sitting that causes these health problems or whether because people have these health problems they sit more than do healthy people.
Sitting uses less energy than standing and it helps to stabilize the body, so we sit to perform fine motor tasks like driving, computer work, creating detailed drawings or fine micro-surgery. However, for many years ergonomists have recommended that sitting is broken up by periodic standing and moving during the day, preferably 1-2 minutes every 20 to 30 minutes. A large body of research has shwon that frequent microbreaks improves levels of comfort, work performance, and reduces the risks of musculoskeletal injuries.
The Perils of Standing
But, standing to work has long known to be problematic, it is more tiring, for men with ischemic heart disease it increases the progression of carotid atherosclerosis because of the additional load on the circulatory system. Prolonged standing at work also increases the risks of varicose veins and accounts for more than one fifth of all cases of working age. So standing all day is unhealthy. The performance of many fine motor skills also is less good when people stand rather than sit. Ergonomists have long recognized that standing to work is more tiring than sitting to work. Standing requires ~20% more energy than sitting. Standing puts greater strain on the circulatory system and on the legs and feet. Consequently, in industry we provide employees with ergonomic anti-fatigue to stand on, with anti-fatigue footwear, and with chairs to allow them to sit down during rest breaks.
We have tested computer use when sitting and standing in different ways (see EHAW). The problem with standing is that when you raise desk height for keyboard/mouse use you need to also raise screen height above the desk or you get neck flexion. Also, for standing computer work the computer fixes the person’s posture there is greater wrist extension and pretty soon people end up leaning which also compromises their wrist posture, thereby increasing the risks of a musculoskeletal disorder like carpal tunnel syndrome.
In our field studies of sit-stand workstations we have found little evidence of dramatic widespread benefits and users only stand for very short-periods (15 minutes or less total per day). Other studies have found that the use of sit-stand stations rapidly declines so that after 1 month a majority of people are sitting all the time, so compliance can be problematic.
Others have proposed a treadmill workstation or a bicycle workstation or an elliptical workstation or a hamster wheel workstation. Treadmill, bicycle and elliptical workstations have been tested and typically shown to decrease computer work performance (typing and mousing slows down and significantly more mistakes are made), although for reading and other non-manual motor tasks the effects are minimal.
Sit-stand workstations are expensive and generally cost-ineffective in addressing the issues to hand. Electric sit-stand workstations also have issue of power supply, energy consumption and higher maintenance.
The bottom line:
Sit to do computer work. Sit using a height-adjustable, downward titling keyboard tray for the best work posture, then every 20 minutes stand for 8 minutes AND MOVE for 2 minutes. The absolute time isn’t critical but about every 20-30 minutes take a posture break and stand and move for a couple of minutes. Simply standing is insufficient. Movement is important to get blood circulation through the muscles. And movement is FREE! Research shows that you don’t need to do vigorous exercise (e.g. jumping jacks) to get the benefits, just walking around is sufficient. So build in a pattern of creating greater movement variety in the workplace (e.g. walk to a printer, water fountain, stand for a meeting, take the stairs, walk around the floor, park a bit further away from the building each day).
So the key is to build frequent movement variety into the normal workday (see CUE - Sit-Stand Programs).
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