Ergonomics that Work
Industrial Hygiene and Environmental Health Office
Fort Detrick, Maryland
Ergonomics is the applied science of equipment design in the workplace to reduce fatigue and discomfort and increase productivity. Cumulative trauma disorders, repetitive stress injuries and work-related musculoskeletal disorders are synonymous terms. All relate to musculoskeletal and nervous system injuries caused by repetitive tasks, forceful exertions, vibrations, compression (pressing against hard surfaces) and/or sustained awkward positions.Fatigue and impairment
In most administrative areas, the source of fatigue or RSIs can often be easily identified by observing the work habits of the individual and/or design of the workstation. For example, individuals who work with a keyboard and/or mouse on top of the desk are at risk of fatigue or RSIs in the back, shoulders, neck, arms and/or wrists. Leaning forward to reach the keyboard puts stress on the lower spine and neck muscles; raising the shoulders to reach the keyboard or mouse will stress the shoulders; and allowing the arm or wrist to lean on the edge of the desk can result in a compression injury. Individuals who sit or slump in a chair without appropriate lumbar spine support risk compressive forces on the lower spine. Even a good task chair can cause pain if it’s not the right size or adjusted properly.
Neck or shoulder fatigue for most individuals often starts mid-day, ending soon after the work day is over, which can be attributed to tilting the head forward to view a monitor that’s too low. Tilting the head backward to view a monitor that’s too high can result in neck pain throughout the workday. Fatigue or pain can also result from twisting the head to read documents or holding the phone between the ear and the shoulder, which can increase stress on the neck and shoulder joints and muscles.
Sitting improperly for long periods can result in back pain, as joints can get stiff and dysfunctional when held in one position for multiple hours each day. Other contributors to back pain include slumping in a chair, lack of support from the chair, improper fit of the chair, improper type of chair for computer use, prolonged sitting without a break and overreaching for the keyboard or mouse.
Chairs that are too high leave the feet dangling, and the constant downward pull on the legs can result in lower back pain. Individuals who keep their chair too low risk stress or injury to the ankles, back and everything in-between as a result of “dropping” into the chair. The shoulders, neck and back are also affected when pushing up from a chair that is too low.Good ergonomics
Many individuals are not aware that fatigue, stress or musculoskeletal disorders are often the result of poor ergonomics. They blame poor sleeping habits, strenuous workouts, gardening, carrying children, etc. While these are certainly contributors, the stressors of a poor ergonomic work environment may be the significant, or even primary, factor in how a worker feels. The following tips for setting up your equipment can be useful in improving the ergonomics of a work environment.Keyboard
- When typing, the shoulders should be relaxed with the keyboard at or slightly below elbow height and parallel with the forearms.
- Keep the wrists in a good neutral (straight) position.
- If the keyboard is on the desktop, ensure the keyboard “feet” are disengaged to avoid wrist flexation.
- For most individuals, a good keyboard/mouse tray is recommended. Adjust the tray in a slight negative slope (i.e., the front of the keyboard is higher than the back, which will help keep the tray off the knees and promote straight wrists).
- Position the mouse as close to the keyboard as possible and at the same height (keyboard/mouse tray users may have to stack the mouse on top of notepads or other material).
- Avoid resting forearms or wrists on a sharp edge or hard surface as this constant, direct pressure (i.e., contact stress) may lead to discomfort or injury.
- If fatigue or soreness occurs in the mousing hand, try using shortcut keys more frequently instead of pointing and clicking the mouse, or switch the mousing hand.
- Use the correct mouse for hand size or task. For example, large hands may become fatigued when handling small mousing devices. Users who work with graphics, plans design/review and other similar tasks should use devices specified for that work (versus devices designed for routine word processing).
- Try an alternative a mouse such as trackball or touchpad, ensuring the device is not awkward to use and does not require overuse of any one part of the hand (e.g., side roller-ball devices).
- Obtain a good, comfortable, appropriate task chair. The chair should be in good condition, equipped with adjustable seat and arm height, not overly contoured, have lumbar support that fits the back well and a seat pan that is deep enough to support the legs.
- Maintain good posture (head, neck, spine are aligned) by sitting back in the chair while keeping the feet flat on the floor (or obtain a good foot support device).
- Get up, move around and stretch frequently.
- Position monitors directly in front of you (never to the side where you must twist your neck or body).
- Adjust the monitor height such that the head does not tilt forward or backward.
- Consider a monitor arm for users who have limited desk space or for very tall personnel (monitors can become unstable when raising them too high to accommodate tall personnel).
- Individuals with corrective eyewear may need a monitor arm to ensure adjustability for their vision needs (which often changes during the day). Also, some individuals with corrective eyewear may need the monitor lower than the hardware allows (to avoid tilting the head backward when looking through the bottom of the eyewear lens).
- Avoid using a notebook computer keyboard since it is usually more compact (forcing the shoulders to be drawn inward) and the monitor is too low.
- When traveling, use an external mouse and keyboard and stack the notebook computer on top of books or furnishings (ensure the computer does not overheat).
- Use care when carrying the computer. Use a wheeled carrier, backpack or a case with a padded strap positioned across the chest.
While this article discusses common ergonomic issues, some individuals may need one-on-one assistance to correct or improve their ergonomic environment, or program managers may need assistance with ergonomic training. This support is available from the Industrial Hygiene Office, local safety professionals and the U.S. Army Public Health Center.FYI
If any of the following is true, evaluation of your work area is needed to resolve or reduce the impact of work-related musculoskeletal disorders:
1. Does fatigue/pain start during the workday?
2. Are personnel rolling/stretching their shoulders and neck after the middle of the workday?
3. Does fatigue/pain go away or diminish after the workday is over?
4. Does fatigue/pain disappear during the weekend and start again during the first workday?
5. Are personnel talking about fatigue/pain or other health problems; are they frequently absent?
6. Have personnel sought surgical treatment for musculoskeletal disorders?