Facility Safety Management

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Ergonomic Evolution
Hand Tools That Fit and Protect The Person Using Them

Almost all work requires the use of the arms and hands. Therefore, most WMSD affect the hands, wrists, elbows, neck and shoulders. Work using the legs can lead to WMSD of the legs, hips, ankles and feet. Some back problems also result from repetitive activities.

Selecting the proper tool for the job and fitting it to the individual using it has become very important for productivity and worker health.

The ergonomic evaluation of work where hand tools are used has helped people to understand that the layout of the workstation, the variety and scheduling of tasks, and the way tools are used, are all factors as important as tool design itself.

Along with common injuries such as cuts, lacerations, and bruises, the frequent and prolonged use of hand tools can cause soreness, aches, pains, and fatigue, which, when ignored, can lead to chronic musculoskeletal injuries (MSIs) of various kinds.

According to the Canadian Centre for Occupational Safety and Health, the most common examples of these work-related musculoskeletal disorders (WMSDs) are tendonitis, tenosynovitis, bursitis, epicondylitis (tennis elbow), carpal tunnel syndrome and de Quervain’s syndrome, a painful disorder affecting the tendons at the base of the thumb.

Several work factors can affect the health and performance of hand tool users, including:

• Static load on arms and upper body muscles;

• Awkward working positions and body postures;

• Tissue compression; and

• Vibration.

Static load or effort occurs when muscles are kept tense and motionless. Examples of static effort include holding the arms elevated, or extended forwards or sideways.

(Try holding your arm straight out in front of you for a few minutes and you will see what we mean. Put any object in your outstretched hand and its weight will add to the static effort exponentially.) Bending and twisting the neck or the whole torso can also increase static load considerably. Add the exertion of force required by hand tools, and static load can increase still further.

Static effort, that is holding any strained position for a period of time, is a particularly undesirable component in any work situation.

Statically loaded muscles are much more vulnerable to fatigue and subsequent injury than muscles that are performing dynamic work involving movement. Furthermore, muscles that are tired by static work take more than 10 times longer to recover from fatigue.

Awkward working positions and body postures: Hand tools are often used where space is limited and access is difficult. When the hand holds and uses a tool in an awkward position, it has less strength and is consequently more susceptible to soreness and eventual injury. If the arm is uncomfortable, the rest of the body is likely to be so as well, because it is natural to compensate for discomfort by trying to re-align the body by bending the back, rounding the shoulders, tilting the neck, and so on.

Awkward positions of the upper body considerably increase the effort needed to complete the task. The resulting fatigue, discomfort, and pain add further to the risk for developing injury.

Tissue compression: As a rule, using a hand tool requires a firm grip. The resulting compression of soft tissue in the palm and fingers may obstruct blood circulation, resulting in numbness and tingling. Blisters are also common due to friction between the palm of the hand and the handle of the tool.

Vibration: Certain heavy tools such as a chipping hammer can produce significant vibration which is responsible for hand-arm vibration syndrome (HAVS), more commonly known as white finger or Raynaud’s syndrome.

Work-related musculoskeletal disorders (WMSDs) are a group of painful disorders of muscles, tendons, and nerves. Carpal tunnel syndrome, tendonitis, thoracic outlet syndrome, and tension neck syndrome are examples. Work activities that are frequent and repetitive, or activities with awkward postures cause these disorders, which may be painful during work or at rest. When work is continued in spite of the developing fatigue, injuries occur.

Force

The force required to do the task also plays an important role in the onset of WMSD. More force equals more muscular effort, and consequently, a longer time is needed to recover between tasks. Since in repetitive work, as a rule, there is not sufficient time for recovery, the more forceful movements develop fatigue much faster.