Choosing & Adjusting an Ergonomic Chair

The human body was not designed to keep still for long periods of time. And yet, the majority of American workers spend hours sitting in a chair while performing job activity. While sitting, the large muscles of the back, shoulders and neck contract to support the active movement of the arms and hands. This constant contraction can lead to fatigue and trigger points in the muscles. A good seating system can help alleviate this risk.

A good seating system allows for adjustability between body types. However, one size does not always fit all. A worker who is petite or larger may need to seek out special chair sizes that accommodate their body frames.

Here are some common adjustments that your office chair should be able to make.


1. Height - The chair should be able to be raised and lowered easily. Height is the first adjustment that should be made. When looking at the proper height of the chair, the elbows should be slightly higher than the work surface (desk or keyboard) so that the elbow is opened slightly greater than 90 degrees. The feet should be placed flat on the floor and the work surface adjusted (such as with an adjustable keyboard tray) if possible. However, if the work surface is not adjustable then the height of the work surface dictates the height of the chair. In this case, a footrest may be necessary to support the feet.

2. Depth of Seat Pan - The seat pan should slide forward and back to accommodate for differences in thigh length. If the seat pan is too shallow then body weight will not be distributed evenly through the thighs. If the seat pan is too deep or too narrow, you will be more likely to sit forward on the edge of the chair rather than taking advantage of the support of the chair back. The seat pan should also be rounded so that sharp edges do not press into the thighs and impede circulation. You should have a space of 2-3 fingers width between the edge of the chair and the back of the knee so that pressure is not placed on the nerves of the leg.

3. Back Support - The back of the chair should be able to be adjusted higher or lower to accommodate for a variety of heights. Proper lumbar support will help maintain the natural curves of the back and reduce the risk of back pain.

4. Seat Pan Tilt - Tilting the pan of the seat will allow you to accommodate for a variety of job tasks while still maintaining lumbar support. It will also allow you to vary working postures throughout the work day. Recent studies are now showing that a mild recline in a supported position is healthy for the back and reduces back pain. Slouching, however, reduces spinal disk height causing wear and tear on the lowest two spinal levels.

5. Arm Rests - The arm rests should raise and lower so that they support the forearms without causing the shoulders to be lifted towards the ears. A good chair will also have arm rests that can swivel or be pushed out of the way if needed. Arm rests should be broad and padded so that the forearm does not press into sharp edges.

6. Chair Base - Any rolling office chair should have a 5-point base of support for safety and stability.


A few more tips to help you remain pain-free while sitting at your desk or workstation -


* Visit an office supply store and take the time to sit in a variety of chairs to get the feel for one that is comfortable for you.

* Look for suppliers who have sample chairs that you can test for several weeks in the office environment.

* Learn to use the adjustments.

* Get up often and stretch frequently to increase circulation and reduce muscle fatigue.

Ergonomic Process - When it Goes Bad

Last week I had the opportunity to work with several injured workers in their office environment. Both spend 8 hours in front of a computer performing extensive keyboard and mouse work. Both are in serious pain with repetitive injuries that cause aching within 30 seconds of sitting down to work. Both have seen doctors, therapists, and had ergonomic interventions with the best equipment issued. One has already been scheduled to undergo a carpal tunnel release in the near future.

Speaking to and observing the work habits of these women has affirmed my belief that ergonomics is a multi-faceted process requiring teamwork to be successful.

• The doctor may diagnose and offer expertise in prescribing medications to calm down the inflammatory process of injury.
  
• The therapists can perform modalities such as massage, ultrasound and the use of heat and cold to promote injury recovery. Skilled in observing how bodies work, they can discover areas of weakness, tightness and muscular imbalances that can be corrected with therapeutic exercise.
  
• The ergonomic specialist can provide the equipment, work-site modifications, and work-style recommendations that create a comfortable and less stressful working environment.
  
• Management can provide a supportive environment that allows healing, promotes employee good-will, but also ensures productivity.
  
• And the injured worker needs to believe in the program and take an active part in their recovery. This is not always an easy thing to do – it requires persistence, even a bit of obsession, to attend medical and therapy appointments, take medications on schedule, change work habits, stretch, take frequent micro-breaks, and use cold packs throughout the day – all while trying to get the job done, frequently under the microscope of management and co-workers who may not believe that an invisible injury can be so painful.

If any aspect of the team process is impaired, recovery may be impaired. Communication and education are critical throughout. So is observation, follow-up, and accepting feedback. My observation of the two young women last week shows how the process can break down in spite of good intentions. It also highlights one of my ergonomic pet peeves – the wrist rest.

Both women had wrist rests in place, and both demonstrated their typing skills using the wrist rest, believing that they were using them correctly and showing me what I wanted to see. Neither had received instruction in the proper use of the wrist rest and they were probably continuing to create inflammation through its improper use.

The wrist rest is not inherently a bad piece of equipment, but it is improperly named. Logically, because of the name, most people feel they need to rest their wrists. Most plant their wrists down on the nice soft surface while typing and feel they are doing a good thing - an ergonomic thing - that will help them prevent injuries. In actuality, they are isolating the work of the fingers from that of the upper arm.

The finger muscles are too small and weak to perform constant movement throughout the day. In addition, the isolated movement is often more extreme than typical to make up for the loss of positioning movement over the keyboard often performed by the shoulder. As the muscles of the fingers and wrist originate at the elbow, pain often begins radiating from the fingers into the elbow.

If ergonomic equipment is issued without warning, - I’ve worked with employees who just showed up one morning to find their work environment changed and ergonomic equipment in place - consent, or instruction in the proper use, it will either be rejected or used in what is thought to be the correct manner. However, the equipment itself is not the answer, but only a tool that enables a worker to be safe if it is used properly.

It would be much better to call the wrist "rest" a wrist "guide" as the wrist should float over it. The wrist rest should "guide" the wrist into the neutral position. It is okay to rest down lightly during typing breaks.

Here are some additional ergonomic keyboard work-method recommendations.

• The hand should be positioned over the keyboard using small shoulder and elbow movements.
  
• The shoulders should be relaxed and not elevated (drawn up towards the ears).
  
• You should be in close enough to the work surface so that your ears, shoulders and elbows are in line.
  
• The work surface should be low enough that the elbows are open slightly greater than 90 degrees.
  
• The fingers should be relaxed and slightly curved as if resting over a ball.
  
• Hit keys lightly with only the minimal amount of force necessary to activate the keys.
  
• Don’t hitch-hike by holding the thumb tensely over the spacebar.

Marji Hajic is an Occupational Therapist and a Certified Hand Therapist practicing in Santa Barbara, California. For more information on hand and upper extremity injuries, prevention and recovery, visit Hand Health Resources.