Risk Factors

Risk factors for Ergonomic Injuries (Cumulative Trauma Disorders, Repetitive Strain or Musculoskeletal Disorders) are conditions that work alone or in combination to gradually cause discomfort and eventual injury. When more than one is present, injuries occur much more quickly. Physically, the risk factors decrease circulation to muscles, tendonsA tendon attaches
a muscle to a bone. and nerves, which need recovery periods to function normally. Resting a muscle, even if another muscle group is used for awhile, allows fresh blood to enter the muscle and sustain its efforts.

Certain lifesty habits (obesity, smoking, lack of exercise) and medical conditions (diabetes, low thyroid, pregnancy, arthritis, previous fracture) also contribute to cumulative / repetitive injuries.

The table below lists common workplace factors that can lead to cumulative / repetitive injuries:

Select from the list below for more information about Ergonomic Risk Factors at Work

Awkward Position
Contact Pressure
Excessive Force
Static Position
Repetition
Vibration and Cold Temperatures
More Tips for Risk Factors at Home and with Hobbies and Sports

Awkward positions require your body to perform work in inefficient ways that strain muscles and tendons. This occurs frequently in your hands, wrists, shoulders or hips. Tendons in these areas glide most easily when they operate in a fairly straight line. When they must move over an angled joint, excess friction and resistance occurs. Eventually this can cause them to become inflamed, roughened and weakened. Also, awkward positions place the muscles in either lengthened or shortened positions which are inefficient for contraction. Thus, the muscles must work harder and become fatigued.

Nerves can also be damaged by awkward positions, especially if they are held for prolonged periods. Pressure within the carpal tunnel of the wrist (containing the median nerve) is lowest in the neutral position (straight) and increases tenfold when you hold your wrist fully up or down. Higher pressure in the canal reduces the blood supply to the nerve.

Considering the number of keystrokes, mouse movements and number of hours you spend at your computer, correct positioning is VERY IMPORTANT. Even slight awkwardness can accumulate over many repetitions to cause an injury.

Poor spinal posture is another example of this risk factor. Slouching in the chair, rounded shoulders and jutting the chin forward all place abnormal stress on the nerves that exit the spine. This will add insult to other risk factors placed on the arms and legs or can directly cause pain radiating into the extremities. Many people with carpal tunnel syndrome, for example, will continue to have pain after surgery because the primary cause of the problem is neck and shoulder positions.

Office Guidelines - Hands and wrists should be in the neutral position, straight and relaxed when typing or mousing. Fingers should be gently curved, not held stiff or up in the air.

At Home - Working on a car or other mechanical device sometimes involves awkward positions. Other examples are cradling the phone with your neck, gripping cleaning tools in awkward positions or using straight gripped hand power tools. Remember, awkward positions contribute to injury whether you are at home or at work.

Back to Top

Contact pressure occurs when a body part rests on a hard object, especially if the body part has little muscle padding. This reduces blood flow, starving the underlying tissues of needed oxygen and nutrients. Waste products such as carbon dioxide and lactic acid accumulate. Over time, this inflames the nerves, muscles and tendons. Localized symptoms can include tingling, numbness, pain or fatigue. Example: Press the palm of your hand against the edge of your desk for a few seconds and then notice the blanching of the skin. The same effect of contact pressure is occurring to deeper tissues.

Office Examples include: Resting wrists on the edge of a desk. Leaning onto elbows placed on the armrest or desktop. Pressure under the thighs close to the back of the knee.

Contact pressure under the thighs occurs when the seat is too high or if the seatpan extends too close to the back of knee. This reduces blood flow to the lower legs.

Home Examples include: Hand tools such as screw drivers and pliers that place pressure in the mid-palm. Handles should reach the base of the palm, where there are muscles to pad the force. Padded handles or gloves can reduce the direct contact pressure. If using gloves, however, make sure that they don’t force you to add extra grip force. Kneeling on hard surfaces is bad news for knees.

Back to Top

Excessive Force is working harder instead of smarter. Don't squeeze the mouse! Drape your fingers over the mouse. Oftentimes we use much more force than is necessary to accomplish a job. Examples of excessive force in offices include: Stabbing the keyboard, clicking the mouse too hard, tapping instead of pushing keys and mouse buttons and squeezing the mouse with a Vulcan Death Grip.

Many knowledge workers use far more force on the keyboard than necessary. The average is three to five times the required force. Over a 30-year career this delivers literally hundreds of extra tons of force to the fingers, wrists and arms! Modern keyboards are much more sensitive than the old manual typewriters, yet some "clackers" remain in every office. Be aware of this habit and correct it to avoid excessive force injuries.

At Home - Keep in mind that excessive force in home activities can also contribute to a Cumulative Trauma Disorder (CTD).Examples include twisting off a jar lid, shoveling dirt or heavy snow and carrying groceries or larger children. Use proper tools, carts and equipment to perform a job safely.

Back to Top

Static Positions keep muscles contracted and tight in the absence of movement. Muscles and tendons are designed to move, not to remain in a fixed position. Blood flow to muscles is highest while moving. A static position keeps the muscles contracted without rest, and blood flow in and out is impeded. Cellular waste products, such as lactic acid, build up.

Office Examples include: holding the wrists up in angled positions (instead of the neutral position); holding thumbs or small fingers up in the air; continuous griping of the mouse without relaxing the hand between movements; holding the shoulders in a tight position for extended periods; and jutting the chin forward for extended periods.

Home Examples include: a tight grip on a phone for prolonged periods; carrying or holding children or shopping bags over long distances; holding a wood or metal piece being worked on instead of using a clamp; and gripping a hammer or power tool constantly during a home project.

Back to Top

Repetition by itself is not a major cause of CTDs in most offices.  Even data entry can be comfortable and safe if the workstation is adjusted correctly, proper techniques are used and adequate breaks are taken. However, other risk factors such as excessive force or awkward position can quickly lead to problems if they are repeated often each day. In other words, if you are at the computer most of the workday, problems with your equipment adjustment, posture and technique will accumulate. Fortunately, most risk factors are correctable and the resultant CTDs preventable. Take breaks more often if you are engaged in a repetitive task. This will improve your productivity over time.

Office Examples: repetitive keyboarding or mousing; looking between a document and the monitor; and frequent reaching for documents in a drawer.

Home Examples: crafts, such as needlework, knitting, carpentry; shoveling dirt or snow for long periods; and certain sports if done frequently.
To sum it up, repetitive activities done correctly and without other risk factors do not usually cause problems. Done incorrectly, these home or work activities can lead to CTDs over time.