HEALTHY COMPUTING GUIDE : CHAIRS

Sep.20, 2008 in Computer, Tips

Healthy Computing Guide : Chairs

Seventy's
photo credit: *Katch*

While talking about a safe and productive computer workstation, the topic of a well-designed and appropriated-adjusted chair comes to our mind naturally. Being an inevitable part of a good workstation, chair offers essential support to the back, legs, buttocks, and arms, along with reducing exposures to awkward postures, contact stress, and forceful exertions. The advantages of using a chair with increased adjustability include ensuring a better fit for the user, providing sufficient support in a variety of sitting postures, and allowing variety of convenient sitting positions throughout the workday. If more than one person is using the chair per day, these points have more relevance. Before selecting a particular chair, try out different ones and finalize on the one that gives the best support. To ensure that the chair will provide adequate support, it is important that you try out different chairs before purchasing one. To create a safe and dynamic workstation, the following parts of the chair have to be observed in detail before selection.

Backrest
Seat
Armrest
Base

The chair should be adjusted while placing the monitor, keyboard and desk in your workstation.

Chair Guidelines

Ensure that the backrest of your chair corresponds to the natural curvature of your spine providing enough support to the lumbar region.
Ensure that the seats of your chair are comfortable enough to allow your feet to rest flat on the floor or footrest.
Ensure that the armrests of your chair are soft allowing your shoulders to relax and elbows to stay close to your body.
Ensure that your chair has a five-leg base with rollers that allow it to move easily on the floor.

Backrest of the chair

Probable Risks

If the backrest of the chair is not designed properly with inadequate size, material, and positioning, the back support will not be sufficient. This would lead to inappropriate postures that cause back pain and fatigue. A chair without suitable or appropriate backrest will fail in supporting your lumbar spine and won’t maintain the natural S-shape curvature of the spine.

Feasible Solutions

Roll up a towel at the lumbar region or place a removable back support cushion for a temporary support if the chair that you use currently doesn’t provide a good lumbar support. This would help you maintain the natural curve of the spine.
You can try using a chair with easily adjustable backrest and which supports the back in all your convenient seating postures. A backrest should have the following features:
- The backrest should have a good lumbar support with adjustable height options for fitting the lower back in different postures. Ensure that the outward curve of the backrest should fit into the small of the back.
- The backrest should have an adjustment that allows the user to recline at least 15 degrees from the vertical. The backrest should lock in place or be tension adjustable so that adequate resistance is ensured to the lower back movement.
- Shorter users can sit with their backs against the backrest without worrying about their knees touching the front edge of the seat pan with the help of a device that enables to move forward and backward. Taller users can sit with their backs against the backrest while supporting their thighs and buttocks fully.

Probable Risks

Too high chairs force the users to work with their feet unsupported and make them move forward in the chair to a position where the back gets zero support which makes it even more difficult for them to maintain the S-shape of the spine. If the user sits continuously in such postures, it can cause fatigue, restricted circulation, swelling, numbness, and pain.

Feasible Solutions

Do make use of a footrest that gives good support to the feet if your seat cannot be lowered.
The seat pan of your chair should be adjustable and of appropriate size to provide support to your body in all your convenient postures. See to it that the seat has the following features:
- The height of the seat should be adjustable especially when there are multiple users. It is ideal if the entire sole of the user’s feet can be rested on the floor with the back portion of the knee slightly higher that the seat of the chair.
- The seat has padded and a rounded, “waterfall” edge.
- The width of the seat should accommodate almost all the hip sizes, at least the majority. For larger users, those with oversize seat pans should be provided.

Probable Risks

It is very uncomfortable for the user to sit in a seat pan that is inappropriately sized. It fails to give enough support to the legs and restrict the whole body movements of the user. Shorter ones place more pressure on the buttocks of the taller users and longer ones place more pressure on the knees of the shorter users minimizing the back support. One that is too small can restrict movement and provide inadequate support. Prolonged use can restrict blood flow to the legs and create irritation and pain.

Feasible Solutions

The depth of the seat pan should be adjustable to support taller users adequately simultaneously allowing shorter users to sit with full support to their back. It should also provide support for most of the thigh without contact between the back of the user’s knee and the front edge of the seat pan.
Always use a footrest, which elevates the knee slightly to relieve pressure on the back of the leg.
Use a chair that is sized to fit small or large users. This is very important if multiple users share the chair.

Probable Risks

Most users tend to sit in awkward postures and thus lack adequate support, if the armrests they use are not adjustable. Let’s discuss the negative points of such armrests:

Armrests that are too low force you to lean over to the side to rest one forearm which in turn results in uneven and awkward postures, fatiguing the neck, shoulders, and back.
Armrests that are too high force you to sit with raised shoulders resulting in muscle tension and fatigue in the neck and shoulders.
Armrests that are too wide force you to reach with the elbow and bend forward for support. This results in pulling the arm from the body and leads to muscle fatigue in the shoulders and neck.
Armrests that are too close restrict movement in and out of the chair.
Armrests that are too large or inappropriately placed may interfere with the positioning of the chair. If the chair cannot be placed close enough to the keyboard, you may have to reach and lean forward in your chair. This in turn leads to fatigue and strain the lower back, arm, and shoulder.
Armrests that are made of hard materials or that have sharp corners can irritate the nerves and blood vessels located in the forearm. This will create pain or tingling in the fingers, hand, and arm.

Feasible Solutions

Some chairs come with armrests that give more discomfort that comfort while working on the computer. Some interfere with your workstation and some others cannot be adjusted properly. Try removing such armrests or at least stop using such armrests. While selecting chairs with armrests, check whether they can be adjusted according to your postures so that they give good support to your lower arm while allowing the upper arm to be close to the body. Armrests that can be properly adjusted should have the following features:

They should have ample width for the users to get in and get out of the chair easily.
They should be close enough to support your lower arms keeping your upper arms close to your torso.
They should be low enough keeping your shoulders relaxed while working on the computer.
They should be high enough to support your lower arms when positioned comfortably at your sides. If the armrests are too low and you find it difficult to adjust them, add padding to the top of the armrests.
They should be large enough to support most of your lower arm. Moreover, ensure that they are small so that they do not interfere with your chair positioning.
Ensure that the armrests are made of soft material and have blunt edges.

It is not necessary that all users should keep armrests to their chairs. It depends on the amount of hours the user spends on the system per day, whether the user has suffered from or is suffering from musculoskeletal disorder (MSD), or whether the user prefers to work with armrests on the chair. But, if you have already decided to have a pair for your chair, do consider all the above-mentioned points before selecting the product.

Probable Risks

If the number of legs of your chair are four or less than four, the support and balance it gives the user will be lesser and hence there are chances of the chair bending and hence the user falling down.
If the casters used for the chair are not good or if the chair doesn’t have casters, the user might find it difficult to position the chair with respect to the desk. Inappropriate choice of casters, or a chair without casters, can make positioning the chair in relation to the desk difficult. This may result in the user bending to access the different components that in turn might lead to muscular strain and fatigue.

Feasible Solutions

Ensure that your chair has a strong, five-legged base.
The casters of the chair should go with the flooring of the workstation. Do ensure that the casters of your chair are proper enough.

Chair Recipe

The chair that you select for your workstation should be easily adjustable.
Ensure that your chair has a strong base with five legs with casters that are good enough to roll over the floor or carpet.
The chair should revolve 360 degrees sot that the user can access items around the workstation without twisting and straining.
It is recommended that the height of the seat is at least 16 inches.
The length of the seat pan should be between 15 inches and 17 inches.
The width of the seat pan should be at least 18 inches. It should have ample room for the user’s thighs.
The edges of the chair should be padded and shaped with soft, but firm material for good support.
It is recommended that the minimum adjustable tilt of the seat pan should be in the range of 5 degrees, both forward and backward.
Try to avoid extremely contoured seats because they restrict different convenient sitting postures and are uncomfortable for many users.
Ensure that the front edge of the seat pan is rounded in a ‘waterfall’ fashion.
Check whether the material used for the seat pan and back is firm, breathable, and resilient.
The depth of the seat pan should be adjustable. Do not go for chairs in which only the back can be tilted forward and backward because they don’t provide adequate adjustment for multiple users. There are chairs with seat pans that can slide forward and backward and have a fixed back. There are some other chairs in which the position of the seat pan is fixed and the backrest moves horizontally forward and backward, so that the effective depth of the seat pan can be adjusted.
The height and width of the backrest should be at least 15 inches and 12 inches respectively. It should be firm enough to provide lumbar support that matches the curve of your lower back.
The backrest of your chair should widen at its base and curve in from the sides to coincide with your body. Ensure that it does not meddle much with your arms.
The backrest should allow you to recline at least 15 degrees and should be able to lock into place for firm support.
The backrest should be high enough to support your upper trunk and neck/shoulder area. A headrest should be provided if the backrest reclines more than about 30 degrees from vertical.
The chair should have removable armrests and the distance between them should be adjustable. The distance between the armrests should be at least 16 inches.
The height of the armrests should be adjustable between 7 inches and 10.5 inches from the seat pan. It is better not to use fixed height armrests, especially for chairs with multiple users.
The length and width of the armrests should be large enough to support your forearm without meddling with the work surface.
The padding of the armrests should be firm and soft.
Normally, chairs for the workstation are designed for users weighing below 275 pounds. For users weighing above 275 pounds, the chair must be designed to support the extra weight.