It appears the majority of jobs are becoming more sedentary, which includes longer durations sitting per day. This poses an ergonomic problem: the more sitting that a person does per day, the more important it is that they are placing their body in a position it can withstand over time. If you sit for 6 hours per day at work (this is a low-ball number for many readers), then you are sitting in the same position for 35% of your waking hours (if you sleep for 7 hours per night). This 35% is outside of the rest of your day which typically includes a lot of sitting, including eating meals, watching TV, driving, and socializing with friends and family. Your work-chair is the first thing to tackle when looking to improve your work ergonomics, but is also one of the hardest and potentially most-expensive parts of the process.
Most work-chairs are not designed for us to sit in them for 30-40 hours per week, over the course of many years. They break down easily, and have limited number of moving parts, making the chair difficult to customize to your individual needs. For my clients, I look for the chair to have these minimal capabilities for the following reasons:
1. Wheeled-chair, with 5 wheels
The wheeled nature of the chair allows you to move it around the room and limit your needs of repetitive reaching. Five wheels allows for easy moving, without much effort from the user.
2. Chair-height adjustments
Most chairs have a lever to go up/down. You need to be able to adjust the height to fit your leg length and desk height needs.
3. Chair-back with tilt capabilities
The chair back should be able to stay firmly erect, or tilt to various degrees and lock in place. Having an upright back allows the neck to stay fairly erect and avoid forward head posturing tendencies. Tilting the back slightly begins to unload the lumbar spine and can be comfortable for users with a history of back pain.
4. Chair-back height and lumbar support
The chair-back should come up to the top of the shoulder blades, which helps minimize the body’s need to dynamically hold the upper/mid back in optimal position for long duration. Quality chairs also have lumbar support which can be changed in height (to customize the location of low back support) as well as depth (for more-or-less support as needed).
5. Seat-pan with depth-changes
The capability to change seat-depth allows for various leg-lengths of individuals. A taller person possibly requires a larger seat depth to account for the longer thigh bones than a shorter person. When sitting upright with good back support, you should have approximately 2-3 finger-widths of space between the edge of the chair and the back of your upper calves.
6. Arm-rests with up/down and in/out features
If you utilize arm-rests, they need to be able to alter in height. The position of the arm rests are different if you are slouching versus sitting up correctly in the chair. If the arm-rests support you when you are slouching, they will provide you with inadequate support when you sit up straight. Also, depending on your body-width, normal arm-rests may be too far away from your body and you will tend to slouch in order to reach them, jeopardizing posture.
These are the minimums I ask clients to have for their work-chairs. You will also want to verify that the chair was designed to withstand full-time sitting, over the course of years. A good chair will have a long, extended full-warranty for their parts, knowing the chair should be able to last the test of time. Once you find the right chair for you, and place yourself in the optimal posture position, THEN it is time to build your environment (the desk, etc) around your optimal. But, it all starts with the chair!
Resources:Smith CFI (specializes in work ergonomics) 620 NE 19th Ave Portland, OR 97232