Ergonomic Rules of Thumb
Strains and sprains are caused by excessive reaching, bending, lifting, gripping,
squatting, or twisting of hands, shoulders, or body. In general, any work performed with
high force, with many repetitions, or in a position that feels awkward is risky. Even a
motion that is harmless in and of itself, like stretching out the arm to grasp an object, or
squeezing a tool, may put the worker at risk of injury if it is repeated over and over.
Following these guidelines will reduce the chance of sprains and strains. You may
need to reposition the work, or redesign the way the job is done, or use a different tool.
Remember: You may not be able to implement all the changes recommended
here. But even partial changes or small changes can reduce injuries.
Guidelines for Hand Work
- Avoid placing needed tools or other items above shoulder height.
- Position items that are used
often within 17 inches of the
worker.
- When movements are repeated
over and over, as in picking
or weeding, allow enough
time in between for adequate
recovery, by having the worker
alternate with a low-repetition
task. For example, a
worker who performs a high repetition
weeding task should
be given other tasks that don't
require repetitive hand motions, like carrying the finished boxes to the loading area.
- Provide seated jobs. Sitting down while working reduces the strain on the lower back
and legs. Standing causes legs to swell (more than walking does). The best jobs are
ones that allow workers to do different types of work, changing from sitting to standing
to walking and back again.
- Allow foot and knee clearances for both standing and sitting workers, so they can get
close to the work.
- Provide floor mats for
standing work stations,
to reduce fatigue.
- For standing work, use
the proper work station
height.
Position items that are used often close to the worker.
Proper work
station height
for light and
heavy work.
Guidelines for
Hand Tools
- When tools require
force, handle size
should allow the worker
to grip all the way
around the handle so
that the forefinger and
thumb overlap by 3/8".
Handle diameter should range
from 1-3/8" for small hands to
2-1/8" for large hands, with an
average of 1-3/4".
- Handles should be covered with
smooth, slip-resistant material
(plastic or rubber). Dual-handled
tools (like shears or pliers) should
have a handle length of at least 4"
and preferably 5". They should
have a spring return to maintain
an open position, and handles that
are almost straight without finger
grooves.
Handle diameter is large enough for small overlap of
thumb and fingers.
Poorly-designed tool: Handle presses into base of palm and requires user to open after each cut (no spring).
Well-designed tool: Handles are long. Spring return keeps
tool open. Handles are covered with rubber or plastic
grip.
Guidelines for Lifting
- Keep lifts between hand level
and shoulder level. Avoid lifts
from the floor or over shoulder
level.
- Provide handles on containers.
- Redesign loads so they can be
lifted close to the body.
- Provide dollies, pallet trucks, or
utility carts for objects that have
to be carried more than a few
feet. Provide roller conveyors for
bags or boxes of vegetables or
chemicals that are handled often. This will reduce the amount of lifting.
- Keep bag or box weight below 50 lbs. Or use the NIOSH Lifting Equation to determine
an acceptable weight. See the Resources section for information on the Lifting
Equation.
Lifting from a good height, between waist and shoulder
level.
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Poorly-designed load: No handles, and load must be carried
too far from the body. |
Better-designed load: Handles are provided and the load
is closer to the body. |
Guidelines for Stooped Work
- Redesign the job to avoid stooped work:
- Attach long handles to tools. (For an example, see pages 9-10.)
- Provide stools. (For an example, see pages 15-16.)
- If stooped work is required, provide employees with other short tasks that require
walking or sitting.
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