Ergonomics is defined as “an applied science concerned with designing and arranging things people use so that the people and things interact most efficiently and safely”. Ergonomics is sometimes known as “human factors” engineering. Ergonomics is the science of fitting the job to the worker. Each year, about 1.8 million workers report musculoskeletal disorders (MSDs), such as carpal tunnel syndrome, tendinitis, and back injuries. Of those workers, about 600,000 need to take time off work because of those injuries. Work-related MSDs occur when the physical capabilities of the worker do not match the physical requirements of the job. Prolonged exposure to ergonomic risk factors can cause damage to a worker’s body and lead to MSDs.
Typically, the focus of ergonomics is on computers and related products, such as computer desks and chairs, as many people use these products for extended periods such as the typical workday. If these products are poorly designed or improperly adjusted for human use, the person using them may suffer unnecessary fatigue, stress, and even injury such as MSDs. Designing workstations and tools to reduce work-related MSDs can help workers stay healthy and companies to reduce or eliminate the high costs associated with MSDs. Although ergonomics applies to many different types of jobs such as construction and manufacturing activities, this article focuses on ergonomics in the office environment, primarily sitting at a desk and using a computer.
Although the Occupational Safety and Health Administration (OSHA) currently does not have standards specific to ergonomics in general, courts have interpreted OSHA's general duty clause to mean that an employer has a legal obligation to provide a workplace free of conditions or activities that either the employer or industry recognizes as hazardous and that cause, or are likely to cause, death or serious physical harm to employees when there is a feasible method to abate the hazard. This includes hazards related to office ergonomics.
Prolonged exposure to ergonomic risk factors in the office environment can cause MSDs. Conditions likely to cause issues associated with MSDs include:
- Excessive repetition of movements that can irritate tendons and increase pressure on nerves (such as using a computer mouse).
- Awkward postures, or unsupported positions that stretch physical limits, can compress nerves and irritate tendons.
- Static postures, or positions that a worker must hold for long periods, can restrict blood flow and damage muscles (such as sitting on a chair at a desk looking at a computer screen using a computer mouse).
- Inadequate recovery time due to overtime, lack of breaks and failure to vary tasks, leave inadequate time for tissue healing.
MSDs can affect nearly all tissue in the body: nerves, tendons, tendon sheaths and muscles. The most frequently affected areas of the body are arms and the back.
The following are practices that should be followed for the various components of working at a desk and computer. Each one of these practices can be incorporated into a Job Safety Analysis (JSA) to educate employees on the proper safety procedures in the office environment.
- Keyboards: Place the keyboard in a position that allows the forearms to be close to horizontal and the wrists to be straight (hand in line with the forearm). If this causes the elbows to be held far out from the side of the body, then re-check the work surface height. Upper arms should be close to the body and relaxed. Some people prefer to have their wrists supported on a wrist rest or the desk could be used to support the wrists. Be careful not to have the wrist extended or bent in an up position.
- Chairs: Adjust the seat tilt so that you are comfortable when you are working on the keyboard. Usually, this will be close to horizontal, but some people prefer the seat tilted slightly forwards. Use a chair with adjustable heights. Raise/lower chair to an appropriate height so that your feet are firmly on a surface for support (floor/footrest), and your knees are bent at a comfortable angle and greater than 90º (i.e., angle behind the knees should be open—don't sit with legs tucked under the chair). Adjust the backrest so that it supports the lower back when you are sitting upright. If needed, a foam block can be placed in the chair to fill the small of the back for support.
- Phones: When using a phone, do not cradle the phone between your head and shoulder. If you need to use your computer at the same time, use a headset or the hands-free/speaker-phone capabilities of the phone, if available.
- Monitors: Set the eye-to-screen distance at the distance that permits you to focus on the screen the easiest. Usually this will be within an arm's length. Set the height of the monitor so that the top of the screen is below eye level and the bottom of the screen can be read without a marked inclination of the head. Usually this means that the center of the screen will need to be near shoulder height. Your eyes should be level with the tool bar. Workers who wear bifocal or multi-focal lenses will need to get a balance between where they see out of their lenses and avoid too much neck flexing. The height of the monitor can be adjusted using a monitor riser. Every hour or so, give your eyes a break from looking at the monitor by focusing on a distant object for several minutes.
- Document Holder: Place the document holder close to the monitor screen in the position that causes the least twisting or inclination of the head. Most workers prefer the document holder to be between the keyboard and the monitor.
- Desks: Adjust the height of the work surface and/or the height of the chair so that the work surface allows your elbows to be bent at 90º, forearms parallel with the floor, wrist straight, shoulders relaxed. Place all controls and task materials within a comfortable reach of both hands so that there is no unnecessary twisting of any part of the body.
- Lighting: Place the monitor to the side of the light source/s, not directly underneath. Try to position desks between rows of lights. If the lighting is fluorescent strip lighting, the sides of the desks should be parallel with the lights. Try not to put the screen near a window. If it is unavoidable, ensure that neither the screen nor the operator faces the window. If the monitor is well away from windows, there are no other sources of bright light and prolonged desk-work is the norm, use a low level of service light of 300 lux. If there are strongly contrasting light levels, then a moderate level of lighting of 400-500 lux may be desirable.
- Using a mouse: A well-designed mouse should not cause undue pressure on the wrist and forearm muscles. A large bulky mouse may keep the wrist continuously bent at an uncomfortable angle. Pressure can be reduced by releasing the mouse at frequent intervals and by selecting a slim-line, low-profile mouse. Keep the mouse as close as possible to the keyboard, elbow bent and close to the body.
- Posture while typing: Change your posture at frequent intervals to minimize fatigue. Avoid awkward postures at the extremes of the joint range, especially the wrists. Take frequent short rest breaks rather than infrequent longer ones. Avoid sharp increases in work rate. Changes should be gradual enough to ensure that the workload does not result in excessive fatigue. After prolonged absences from work, the overall duration of periods of keyboard work should be increased gradually if conditions permit.
There are no specific training requirements for ergonomics. However, employees who have been trained to identify and avoid ergonomic hazards are better able to avoid those hazards, leading to a safer workplace. To get the most out of an ergonomics program, an employer can train workers on:
- Common MSDs and their signs and symptoms.
- The importance of reporting MSDs, and signs and symptoms, as soon as possible.
- How to report MSDs in the workplace.
- Risk factors and work activities associated with MSDs hazards.
Identifying ergonomic hazards and controls can easily be done with the help of creating a JSA worksheet or Activity Hazard Analysis (AHA) template through JSABuilder.com. This online JSA software walks users through the steps of creating JSAs and AHAs. Set up a free trial account today and follow us on Twitter @JSABuilder, where we Tweet about Health and Safety, provide Safety tips, and updates on current Health and Safety topics.