Friday, November 30, 2018 Gregory Santo
Are shovels "ergonomically" designed?
The design of shovels and spades did not come from an ergonomist's drawing board. They are basic tools that have evolved over many centuries. Thousands of years of experience with such common tools has resulted in a great variety of shovels and spades being developed to meet numerous needs.
In general, a shovel is a tool used to dig as well as to move loose, granular materials (like dirt, gravel, grain, or snow) from one spot to another. A spade is a tool used for digging straight-edged holes or trenches, slicing and lifting sod, and edging flower beds or lawns.
The most important features in the selection of a shovel include:
- Handle type
- Blade size and shape
Why is the weight of the shovel important?
The amount of muscular effort required in shoveling depends on:
- Total weight of the shovel,
- Weight of the load it carries,
- How far the load is from the body, and
- Where the hands are placed on the handle.
Reducing the weight of the shovel, which is unproductive weight, increases shoveling efficiency.
The weight of the shovel typically ranges from 3.3 lb. to 6.6 lb. The weight depends in part on the type and weight of material (e.g., steel, aluminum, plastic) that is suitable for the intended use. For example, a light shovel (e.g. 3 lb.) may be suitable for shoveling light snow but a heavier, sturdier shovel (6.5 lb.) may be needed to shovel stones or coal.
Why is the type and length of the shaft important?
There are two conflicting opinions regarding the overall length of a shovel. Longer shafts (up to chest height) ease the strain on back muscles by reducing the amount of bending required. Shorter lengths result in better stability when transferring the load. These two factors have to be carefully balanced when deciding which shovel to choose for the task.
In general, when the blade is placed on the ground, the total length (blade plus shaft and handle) should be approximately to elbow height (when arms are at your side). Spades used for digging holes or cutting turf are usually longer than shovels.
For snow shoveling, shovel shafts are now available with bends in the shaft or a second handle (usually mid-shaft) which are intended to decrease the amount of forward back-bending required. There are no studies that specifically recommend the use of bent-shafted shovels or mid-shaft handles, although some users do indicate they feel these shovels reduce back discomfort.
Some of these shovels are also designed to push snow versus lift it. Take the time to determine what motions you need to perform and what type of shovel and design will be best for you.
Ultimately, the shovel shaft should be constructed to be strong and light. Fiberglass shafts and/or handles are often lighter and stronger than traditional wood shafts.
There are some models that use a fulcrum principle with a wheel base to move snow.
For summer shoveling, a non-slip handle can lower the force you need to hold the tool, especially in hot conditions where your sweat may interfere with your grip.
Why is the size and shape of the blade important?
Selection of blade size and shape should depend on the hardness, density (or weight), and the stability of the materials being shoveled. The less dense the material, the larger the blade size.
- Use triangular or round blades with long handles for sand and dry earth.
- Use square blades with short handles for coarse-grained materials such as gravel, coal, or ore.
- Use a smaller blade (shovel heads) to minimize the weight of material when lifting.
- Use a blade that has rolled step on the top (it can be triangular, round, or straight at the bottom) for digging in hard earth. These shovels/spades allow the users to apply foot pressure to push the blade into the earth. This action substantially reduces strain on upper body and lower back.
What factors should I consider while designing shoveling tasks?
The major components of shoveling and digging tasks are:
- shoveling rates
- shovel loads
- throw height
- throw distance
What is the recommended rate for shoveling?
The most efficient shoveling rate is estimated at about 18-21 scoops per minute. However, fatigue builds up over a short time at this rate. Therefore, the recommended rate for continuous shoveling tasks is usually considered to be around 15 scoops per minute. Tasks involving continuous shoveling at this rate should not be carried on longer than fifteen minutes at a time. The shoveling rate per minute will also depend on how easily the shovel can be inserted into the material being moved (e.g., grain, snow, gravel, compacted earth), the stability of the material being moved, and the weight of the material.
The length of the rest break depends on many factors. Since most shoveling is done outdoors, consideration for the prevailing conditions is very important. In the more extreme conditions such as very hot and humid, or very cold and windy, 15 minutes of shoveling should be followed by 15 minutes of rest.
What is the recommended weight of the load to be lifted?
The load lifted should be adjusted according to the shoveling rate. For a high rate of shoveling (about 15 scoops per minute) the total weight (weight of a shovel plus a shovel load) should not exceed 10 to 15 lb. For higher weights, a lower rate of scoops per minute is suggested for 6 to 8 scoops per minute. In addition, the need for precise placement of the load decreases the amount to be lifted because it takes more time and effort to aim the load at a selected location.
What is the recommended throw height and distance?
Throw height should not exceed approximately 4 feet. The optimal throw distance is about 3 feet. The load should be reduced if the task requires a longer throw.
There are also guidelines for maximum workloads for continuous shoveling.
Maximum Amount of Material Transported, Continuous Work
Weight Per Minute
Per 15 Minutes
Lifts up to 40 in. above the ground - compact, non-critical load placement.
Lift routinely above 40 in. above the ground
Very precise load placement or shifting load (reduces possible lifting frequency and weight per lift).
What should you do before shoveling?
Shoveling is strenuous work and hard on both the heart and the back. For older people or persons with a history of back or heart problems it might be better to avoid this job altogether. Shoveling is especially difficult under extreme weather conditions (cold winter, hot summer). Even for the physically fit, warm-up exercises before starting shoveling is highly recommended. Flexing and stretching exercises warm and loosen the muscles and prepare them for the job ahead.
What are some other basic safety tips to know when shoveling?
- Always contact your local utility providers (Dial 811) before digging to determine the location of any cables, power lines, gas pipelines, water pipes, etc. that may be below ground. In some jurisdictions, it may be against the law to dig without locating certain services. In addition, the homeowner or contractor could be liable for any damages caused.
- Wear the proper protective clothing; safety footwear, gloves, long pants if necessary
- Allow for safe distance between people if you are working with other people.
What are guidelines for shoveling?
- Keep feet wide apart. Place front foot close to shovel.
- Put weight on front foot. Use leg to push shove
- Shift weight to rear foot. Keep load close to body.
- Turn feet in direction of throw.
- Push spade down using leg muscle.
- Slide load close to body. Ensure load is loose from ground before lifting.
Some content provided by the Canadian Centre for Occupational Safety and Health
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