Sit right at your computer – includes ergonomic checklist

In the decade since we last discussed the health hazards of using video display terminals (VDTs), rapid advances in microchip technology have produced yet more changes in the ways that people work, play, shop and conduct other activities, along with increasing health problems from sitting all day staring at flickering screens and punching keyboards.

Computer use brings ergonomic health concerns

Ergonomics — a term barely heard until recently — has become a trendy catchword used to sell products such as car seats (“ergonomically perfect for human backs”) or office chairs (“with optimal ergonomic comfort”). The science of ergonomics deals with work environments and the relationship between humans and their equipment. Biomechanical principles are used to design machinery and tools that are safer and healthier for those operating them. For example, keyboards and other fine hand-tools are best used with straight wrists in a “neutral” position to lessen injury risks. Additional ergonomic features to consider include back posture, head-tilt, the heights and types of work surfaces, seating arrangements, visual angles and illumination. (Tools for women should have different dimensions from those used by men.)

Ergonomic concerns about VDT use surfaced in the 1970s because of a dramatic increase in operator complaints of muscle strain, particularly in the back, neck, shoulders and wrists — partly blamed on the nonstop tempo of today’s keyboarding. Rapid action of fingers on keyboards for hours on end can inflame parts of the hand and/or wrist, pressing on nerves, possibly producing pain and tingling. Other health problems arise because modern equipment eliminates many of the movements previously entailed in keyboarding, abolishing the opportunity to move and stretch the muscles.

“Repetitive strain injury” a mysterious modern malady

U.S. statistics suggest that musculoskeletal aiments rank first among job-related injuries and compensation claims. The U.S. National Institute for Occupational Safety and Health found the incidence of work-related musculoskeletal disorders in some occupations, particularly among newspaper reporters, as high as 40 per cent.

Repetitive strain injury describes work-linked musculoskeletal disorders involving pain, discomfort and muscular weakness, sometimes along with tissue swelling. (Alternate terms include “overuse syndrome” and “cumulative trauma disorder.”) The rise in musculoskeletal disorders is attributed to poor posture, inefficient work habits, lack of ergonomic planning and repetitive movements (as in keyboarding or assembling small parts). But accurate diagnosis is tricky because, apart from occasional swelling, it depends on subjective descriptions, rather than detectable or measurable signs of injury. Improving posture and muscle tone (with appropriate exercise) can reduce the incidence of muscle strain.

Prevention is a must because many of those afflicted can take ages — weeks or months — to recover, and the condition often worsens or improves without rhyme or reason. Therapy includes physiotherapy, biofeedback, movement retraining, EMG (electromyography) and other strategies. (One Toronto newspaper journalist had to switch to a costly, slow, voiceactivated computer rather than a faster keyboard-operated one.) People must also take care not to reinjure themselves.

Keyboarders need frequent mobility breaks

Frequent breaks for muscle stretching and mental variety are vital for VDT users, not only to move the muscles but also to reduce fatigue and promote social interaction. Short, frequent breaks seem better than occasional long ones. Although there are no strict rules, many ergonomists suggest a five to 10 minute break after each hour of computer work. Studies show that even 10 per cent of VDT working time can be spent in rest periods without lowering productivity. On the contrary, frequent breaks increase efficiency. Pauses are best individually negotiated rather than by strict protocol.

Flexibility is the key to ergonomic health

Although immobility is one factor in muscular strain, badly placed equipment and poor design contribute. “In wading through the mass of supposedly ergonomic products,” warns one expert, “remember that in this evolving field the best bet is: buyer beware!” There’s no need to spend a fortune on office improvements — simply ensuring good adjustability and reorganizing existing furniture, perhaps purchasing a few inexpensive items (such as footrests, lamps or document holders) may suffice to make VDT use ergonomically healthier. The idea is to arrange things so that the body works in a manner least likely to cause muscular strain. Parameters set by American National Standards Institute emphasize that VDT tables and chairs should be easily adjustable, as operators differ in size and shape. Document holders and viewing screens should be adjustable and keyboards detachable — so they can be put in any desired position.

Sitting, especially for hours on end, is very hard on human backs and exerts a far greater load on the spine than standing still or walking. The right chair is a key element in ergonomic wellbeing. Thighs should be roughly parallel to the floor, feet flat on the floor or on a footrest. Seating too low pressures the thighs; having the seat pan too high puts unwanted pressure on the back of the knees.

To avoid keyboard grief, make sure wrists are not bent too far up, down or sideways. Prolonged wrist extension (palm down, back of hand turned upward) can cause pain and musculoskeletal disorders such as carpal tunnel syndrome. While activating keys does not usually stress the hands, uninterrupted, long-term, rapid keying, done in awkward positions, can cause muscle strain in susceptible individuals.

Avoid eye strain from VDT use

Although not likely to cause permanent vision problems, many computer inputters complain of burning eyes, itchiness, irritation, fatigue and dry eyes that feel “gritty.” Concentrating on VDT screens reduces blinking, which can dry the eyes, particularly in contact lens wearers. VDT users should try to blink more frequently and take occasional eye rests (a momentary switch is all that is needed). The viewing distance used at VDTs may require corrective lenses different from those for everyday activities. Wearers of bifocals who use the reading portion of their lenses to view the screen can force their necks into awkward positions that strain the neck and shoulder muscles. Poor illumination, illegible manuscripts and glare (from reflected lights, incorrect lighting or shiny surfaces) can contribute to eye strain. Since VDT users continually glance from document to screen to keyboard, all three are best arranged in the same plane of focus, to reduce the need for continual eye-focussing changes.


For more information: consult a practicing ergonomist; the Canadian Centre for Occupational Health and Safety 1-800-263-8466; the Institute for Work and Health 416/927-2027. Read Voluntary Office Guidelines published by the privatesector Canadian Standards Association. (Watch for more information on musculoskeletal disorders in the next issue of Health News.)

Ergonomic checklist for healthy VDT/computer use

Workstation layout

* Make sure all parts of the workstation are easily reachable without impediment, to avoid undue twisting of neck or trunk.

* Design workstation to suit all tasks done.

* Adjust workstation to fit the body.

* Arrange working surfaces at correct height/position for eyes and posture, with no sharp edges.

* Place keyboard near the table edge and make it fully movable in any direction, detachable from screen to permit comfortable working position.

* Tilt slightly forward to avoid awkward wrist/hand positions.

* Be sure the keyboard is thick enough for comfortable arm positioning (less than 30 mm thick at the home row of keys).

* Use a document holder (adjustable and detachable).

* Be sure documents can be easily manipulated, with enough space for large ones.


* Try to keep head and neck in one line, head not jutting forward, with chin down.

* If using the telephone while at the VDT, use a headset or speaker-phone to avoid neck and head strain (while cradling the receiver on the shoulders).

* Support the back; share body load as evenly as possible.

* Take frequent postural pauses — move about, stretch the muscles.

Arms and legs

* Minimize strain by keeping wrists and hands as straight as possible.

* Place forearms parallel with the floor or angled slightly downward. (This can be achieved by lowering the desk to suit the user or, with a fixed-height desk, by raising the chair.)

* Legs should be able to wriggle and move without hitting furniture.

* Keep feet flat on floor or on a footrest (big enough for both feet).

* Knees should be at about a 90[degrees] angle, thighs parallel to floor, body weight not restricting circulation, with ample leg room.


* Seats should be firm and upholstered.

* Seat tilt is best horizontal or a little backwards, to prevent sliding forwards.

* Seats should allow clearance for the thigh muscle; the back of the knee should not touch the seat. Seat pan height is adjusted to put user’s weight on the buttocks, not the thighs.

* Be sure chairs are easily adjustable when seated.

* Backrests should adjust up, down, backwards and forwards for good lumbar support, and fit the small of the back to support the spine, with users sitting upright while keying — but ergonomists disagree about the best type.

* For chair mobility, wheels or castors can be fitted (hard castors for soft floors, soft for hard floors). For tasks involving lateral movements, seats should swivel.

Screens (if applicable)

* Put the screen at a comfortable reading distance.

* When looking straight ahead, be sure user sees the top edge of the screen.

* Ensure that characters are easily legible.

* Adjust screen contrast and brightness as needed, minimize glare.

* Make sure screen does not flicker and has good contrast.

COPYRIGHT 1994 Strategic Inc. Communications Ltd.

COPYRIGHT 2004 Gale Group

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