Dynamics of The Erogonomic Chair

For most of us, as the winter months set in, we spend less time outside and more time inside.... sitting. We sit to have breakfast, sit on our drive into work or school, sit in our office and then come home after work to sit to watch TV. The detrimental effects of a sedentary lifestyle are well-documented and more effort needs to be placed on physical activity. But we can't ignore that we do need to sit - some of us for many hours. So, just as those who run a lot buy the best shoes, those of us who sit a lot must find the best in chair adjustability, support and comfort. Sitting in itself is a specialized activity and changes based on our job tasks. Architects, dentists, administrators all require unique features to their chairs. There are, however, key features that all chairs should possess, with the most important being stability and adjustability.

Stability
The chair is our base of support and affects all other surroundings. The chair should be positioned on a five point base that moves easily around the workstation. Selected chairs should not make the tasks more difficult so it is important to consider the job tasks and the surroundings. Sometimes chairs with castors or wheels are used when a stable and stationary work position would be better. If chairs with casters are needed, choose ones that match the type of flooring you have (carpeting or hard floors).

Adjustability
Adjustability of the chair is the most important. Not only do your tasks differ throughout the day but the user of the chair may change as well. The chair needs to be adjusted to fit your body dimensions and your tasks throughout the day. At a minimum, the seat height, the backrest, seat pan and arm rests should all be adjustable. To ensure your chair is properly adjusted, refer to the diagram below.

SEAT HEIGHT - Thighs horizontal to the floor or sloping slightly downward, knee angle 90°-100° and feet flat on the floor or foot rest.SEAT ANGLE - The seat angle should be varied from forward to backward throughout the day.SEAT DEPTH - Leave approximately a 3 finger width of clearance between the back of the knee and the front of the seat.BACK REST HEIGHT - The lumbar support should be about 2 inches above the waist.BACK REST ANGLE - Locked at greater than 90° so the angle between your upper body and thighs is greater than 90°. Your back should be in contact with the backrest of your chair at all times.TILT TENSION - Adjust to suit your weight so that the chair moves with you in a controlled and effortless manner as you shift your weight forward and backward.ARM RESTS - Adjust to lightly support your forearms to reduce muscle activity in your neck and shoulders without causing your shoulders to rise. They should not prevent you from getting close to the work surface.KEYBOARD - Adjust so that the keyboard is 2 to 3 CM below your elbow height when sitting. Elbows should be at your sides and bent at 90°. The F6 key should be centered to your body.MONITOR HEIGHT - Should be placed so that the top of the screen is at an eye level so that your eyes rest on the upper third of the screen. Monitor should be centered to your body.MONITOR DISTANCE - Approximately an arm's length from your eyes.

Brenda Rusnak is a health care specialist who writes about health-aging and prevention.

For more information about healthy-aging and Brenda Rusnak, check her out on Inside Toronto.

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