A 2003-2004 U.S. survey concluded that Americans spend more than half of their day sitting. That number may not be news, but the fact that all that sitting may actually shorten one’s life span is frightening information. Several recent studies have suggested that people who spend most of their day sitting may have shorter life spans. While the research is still in its early stages and experts have yet to determine how many hours a day is too much, it would be wise for all of us to find ways to break up long periods of sitting.
Canadian researchers published a study last year that tracked more than 17,000 people for 12 years. This study found that people who sat more had a higher risk of death, and that this was true even if they regularly exercised. In an editorial published in the British Journal of Sports Medicine (Jan 2010), author Elin Ekblom-Bak suggests that "after four hours of sitting, the body starts to send harmful signals" that cause the genes regulating glucose and fat in the body to shut down.
From an ergonomic and health viewpoint, the need for movement over the course of the day is not new information. Science has known that constrained seating is bad for one’s health for more than 40 years. Workers who use a fixed seated position all day experience more discomfort and chronic disorders (Graf et al, 1993, 1995). Health problems that can arise from long hours in a stationary position include arthritis, inflamed tendons, chronic joint degeneration and impaired circulation (Grandjean, 1987). As early as 1975, research indicated that workers over 35 that spend more than half their time sitting had a higher rate of herniated discs (Kelsey, 1975).
What does this mean to you? Stated quite simply, get up off your duff and move! Take mini-breaks, five minute breaks every hour or so. Change the seat angle, back angle or tilt of your chair throughout the day or better yet, leave the tilt lock off and let the chair move when you move. Use of a chair with a dynamic mechanism, such as the Humanscale Freedom Chair, Steelcase Leap, or Knoll Life Chair allow for regular position shifts without any active thought on the part of the user.
Better yet, stand part of the day. Research done by Dr. Mark Benden of Texas A&M University, suggests that standing at least two hours a day improves energy levels, productivity and can even assist in weight control. Standing two hours a day can burn up to 280 calories daily (depending on body size and other factors); over the period of a year, this can add up to a weight loss of 20 lbs.
Setting up your workstation so you can stand part of the day can be done in a number of ways. The most direct approach is to use an electric, height adjustable desk and just push your chair out of the way when you wish to work standing. Alternatively, a higher work surface can be used with a tall chair, or a standard desk can be used with a monitor arm and keyboard tray mechanism that offers enough height adjustment range to allow you to work sitting or standing.
Graf, M, Guggenbuhl, U. and Krueger, H. (1993) Investigations on the effects of seat shape and slope on posture, comfort and back muscle activity. International Journal of Industrial Ergonomics, 12 (1-2), 91-103.
Graf, M, Guggenbuhl, U. and Krueger, H. (1995) An assessment of seated activity and postures at five workplaces. International Journal of Industrial Ergonomics, 15 (2), 81-90.
Grandjean, E. (1987). Ergonomics in computerized offices. London: Taylor and Francis. 96-156.
Kelsey J. L. (1975). An epidemiological study of the relationship between occupations and acute herniated lumbar intervertebral discs. Int J Epidemiology. 4(3): 197-205.