Ergonomics in action: a practical guide to the workplace
by Céline McKeown
£30 softback 256 pages
ISBN 978 0 901357 47 2
Hand or arm injuries following the use of tools may indicate
inappropriate tool design or improper use. Such injuries can range
from something as simple as a callus or blister, to something more
severe such as a ULD. In most instances, injuries can be avoided by
ensuring that tools are properly designed, taking both the user and
the task into account.
One of the most common complaints made by workers is that they have
to bend their wrist when using tools. For some reason, designers
have until recently designed most tools with straight handles and
heads. As a result, when the tool user works on or against a flat
surface, they will usually have to bend their wrist.
The user experiences a loss of grip strength from working with a
bent wrist. To overcome this problem, and to control the tool
fully, the pressure of the grip may be increased. Increasing the
grip pressure will speed up the rate at which the muscles fatigue.
Therefore, to avoid the reduction of grip strength and subsequent
acceleration of muscle fatigue, maintaining a straight wrist should
be a primary design and selection consideration. This can be
achieved easily in many work situations by bending the handle (see
In some situations, bending of the wrist can be eliminated by
providing a pistol grip tool where the handle is bent by 70–90º.
However, this design is only acceptable if used in an appropriate
orientation. In general, pistol grip tools should only be used when
the tool axis is horizontal. If the tool axis is vertical or the
force is applied perpendicularly to the work plane, a straight grip
should be used. Examples of wrist posture, tool design and
orientation of use are shown below.
If users have to work with a tool which has a smooth, hard handle
constructed of a material such as flat metal or plastic, they may
experience difficulty in stopping their hand from sliding across
the handle as they apply force. To prevent the hand from moving,
the user will increase the pressure of the grip – this situation is
made worse if their hands are hot and sweaty.
Care should be taken if the handle is designed with flutes or
ridges (eg a screwdriver). If these flutes or ridges are too deep
or have sharp edges, they may increase the pressure placed on the
soft tissue of the hand when the user grips the handle and this may
result in discomfort and pain. Soft oval indents on a handle are
preferable – they allow improved purchase without causing pressure
If handles are made of metal, they may remain cold throughout
the course of the shift. Exposure to colder temperatures may
increase the possibility of a user developing a ULD, so the use of
metals in handle design should be avoided.
It is recommended that soft, compliant and textured materials
are used on handles so that they are easier to grip, although care
needs to be taken that these cannot be damaged easily, subsequently
presenting sharp edges.
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