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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 great variety of shovels and spades being developed to meet numerous needs.
In general, a
However, in North America, the term shovel tends to be used for both shovels and spades. When selecting the right shovel for the task, ergonomic considerations are essential.
The most important features in the selection of a shovel include:
The amount of muscular effort required in shovelling depends on:
Reducing the weight of the shovel, which is unproductive weight, increases shovelling efficiency.
The weight of the shovel typically ranges from 1.5 to 3 kg (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., 1.5 kg (3 lb)) may be suitable for shovelling light snow but a heavier, sturdier shovel (e.g., 3 kg (6.5 lb)) may be needed to shovel stones or coal.
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 shovelling in particular, 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.
For summer shovelling, 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.
Selection of blade size and shape should depend on the hardness, density (or weight), and the stability of the materials being shovelled. The less dense the material, the larger the blade size.
The major components of shovelling and digging tasks are:
The most efficient shovelling 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 shovelling tasks is usually considered to be around 15 scoops per minute. Tasks involving continuous shovelling at this rate should not be carried on longer than fifteen minutes at a time. The shovelling 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 shovelling 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 shovelling should be followed by 15 minutes of rest.
The load lifted should be adjusted according to the shovelling rate. For a high rate of shovelling (about 15 scoops per minute) the total weight (weight of a shovel plus a shovel load) should not exceed 5 to 7 kg (about 10 to 15 lb). For higher weights, a lower rate of scoops per minute is suggested (e.g., 8 kg 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.
Throw height should not exceed 1.3 meters (approximately 4 feet). The optimal throw distance is slightly over l metre (about 3 feet). The load should be reduced if the task requires a longer throw.
There are also guidelines for maximum workloads for continuous shovelling. This table is an example of such suggested by the Kodak Company.
|Maximum Amount of Material |
Transported, Continuous Work
|Weight Per Minute||Total Weight Per 15 Minutes||Conditions|
|80-90||175-200||750||1,650||Lifts up to 100 cm (40 in.) above the ground - compact, non-critical load placement.|
|55-65||120-145||530||1,165||Lift routinely above 100 cm (40 in.) above the ground|
|22-33||50-75||245||535||Very precise load placement or shifting load (reduces possible lifting frequency and weight per lift).|
Shovelling 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. Shovelling is especially difficult under extreme weather conditions (cold winter, hot summer). Even for the physically fit, warm-up exercises before starting shovelling is highly recommended. Flexing and stretching exercises warm and loosen the muscles and prepare them for the job ahead.