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Occupational overuse syndrome (OOS)

OOS is also called repetitive strain injury, repetitive motion disorders and cumulative trauma disorders. This terminology has been applied to different soft tissue and inflammatory joint conditions, including tendonitis, tenosynovitis, nerve entrapment syndromes (e.g. radial, ulnar, etc.), epicondylitis, muscular sprain and strains, carpal and radial tunnel syndrome, bursitis and rheumatoid and arthritic conditions, particularly when associated with some occupational exposures. Symptoms appear gradually and do not relate to a specific cause.

All of these conditions have similar symptoms – pain (often diffuse and burning in nature), tingling, numbness and swelling in the joints and muscles (generally of the hand, arm and forearm). Tenderness and autonomic dysfunction are sometimes present. Other symptoms include lack of movement and pain in the shoulder and neck regions. Static muscle loading (maintaining the same posture and position of a joint) has been shown to be a contributing factor, as well as repetitive movements, and exposure to vibration and cold temperatures.

Important contributing risk factors for the development of musculoskeletal conditions associated with office work include working hours, work distribution and pace, repetitive and monotonous tasks and stressful postures such as wrist flexion, extension and/or deviation, and upper arm elevation. Research has shown it is better for workers to have frequent short breaks rather than fewer longer breaks during their working day. Workers who completed repetitive manual tasks were found to be particularly at risk of suffering radial tunnel syndrome.

Work duties within many industries involve repetitive movements. Hand and wrist tasks can be considered repetitive if the basic action is repeated within 30 seconds.

So, for example, computer mouse usage qualifies as a repetitive task. Many software programs are ‘mouse driven’, particularly those involving data entry and text or graphics editing tasks.

The amount of time spent completing repetitive tasks over the working day is significant but the body can recover from stressful work tasks if there is enough variation in the tasks and/or “rest” time. Muscle and joint recovery is dependent on blood supply reaching tissues. If blood supply to a group of muscles or a joint is reduced or restricted, for example, due to an increase in the external or internal pressure at the carpal tunnel of the wrist, OOS symptoms may result. Workers who are exposed to vibration and use power grips associated with their work are also at risk of developing OOS. Muscles repair and recover faster than ligaments, tendons and nerves following stress and injury; however, the amount of time for each person to recover from physical “stress” varies.

The repetitive use of a mouse can result in OOS symptoms, especially if the work is mainly computer and mouse based. This is particularly relevant for editing tasks when the user “scrolls” through screens of data to effect changes, or “drags” and “clicks” the mouse buttons repeatedly. In this case, the small muscles of the hands and fingers complete most of the work, whilst the wrist, elbow, shoulder and neck are held in virtually the same position. This may lead to pain, strain and stiffness in the muscles and joints.

Carpal Tunnel Syndrome
The carpal tunnel is the area under a ligament (a tough, elastic band of tissue that connects bones) in front of the wrist. Repetitive movements of the hand and wrist can cause inflammation of structures (such as tendons and their coverings) that surround the median nerve. The inflammation may compress this nerve, producing numbness, tingling, and pain in the first three fingers and the thumb side of the hand - a condition known as carpal tunnel syndrome.

Causes and risk factors for computer users

• ignorance of the warning signs or risk factors for injury.
• intensive computer use (deadlines, reports, projects).
• lack of frequent, regular rest breaks.
• poor posture.
• incorrect keyboard and / or mouse height or positioning.
• Resting your wrist on the work surface or wrist rest with keying or mousing.
• keying or mousing with wrist bent upwards, rather than being straight.
• stretching and twisting to reach keys while your wrists are anchored on a wrist rest/desktop.
• stretching and twisting while mousing with your wrist anchored on a wrist rest/desktop.

Warning signs

• numbness and tingling (pins and needles) of the palm, the thumb, index, middle and half of the ring finger.
• pain and aching in the same area of the hands and continuing up into the forearm may also occur.
• awakening with a tingling sensation and the need to "shake out" the hands to recover normal sensation.
• hands falling asleep.
• cold hands.
• difficulty using hands, such as holding a cup, turning pages in a book and turning a door knob.

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