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, larger muscle groups from working at maximum efficiencies. Blood flow is impaired and the rate of fatigue increases if exertion is increased in the weaker, smaller muscles. In the computer work they include typing with bent wrists, turning the head to the side to view the monitor, reaching up and over the keyboard to use the mouse and leaning over to type in data from papers laying flat on the desktop. In office work these include slouching or leaning forward in the chair, cradling the phone between the ear and the shoulder, elevating the arms when writing on a work surface that is too high and bending at the waist to load copy machines. Typically the awkward postures include repeated or prolonged reaching, twisting, working overhead, bending, kneeling, squatting and holding fixed positions or pinch grips. These may have effect on various areas of the body like hands, wrist, shoulders, arms, back, neck and knees. These postures also may be caused by using poorly designed or arranged workstations, tools and equipment and poor work practices.

 

Mechanical contact stress causes injuries when a hard or sharp surface or object press into soft tissues like tendons, nerves and blood vessels, which can cause damage which over time result to injury of serious levels. Such injuries in computer work include resting wrists on the desk edges while typing or using the mouse, leaning the elbows on hard chair armrests or work surfaces and typing with palms resting on the hard lip of a keyboard tray. In the office work these include using rubber stamps with handles that press into the palm of the hand, using scissors with hard, metal handles and sitting in a chair that places pressure on the backs of the thighs.

 

Visual efforts can cause injuries in various ways. People sometimes assume awkward postures or experience eye strain fatigue because it is hard for them to see their work when the lighting is bad, the work is too far away or materials are blocking the field of vision. This causes the affected person to bend, reach, twist or hold fixed positions. Also handling and assembling very small parts and materials or performing extremely precise tasks may contribute to eye strain and awkward postures.

 

The same types of motions are performed over and over again using the same muscles, tendons or joints in repetitive work. The pace of work, the recovery time provide which is the number and length of muscle relaxation breaks, and the amount of variety in work tasks affect the amount of repetition. People performing a task, machines or administrative procedures can control the pace or the work being done. The example of jobs involving machine-controlled pace include working on assembly, packaging and quality control lines. Administratively controlled pace tasks include those tasks that are linked to performance or incentives. When repetitious jobs involve awkward postures or forceful exertions, the risk of injury is greater. Injury may also develop when highly repetitive jobs are combined with low force exertions such as light assembly tasks involving the hands, wrists, elbow and shoulders.

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