The most crucial aspect of ergonomics to to fit the demands of a job to YOU. The demands of a job like breaking up hard soils, cutting through awkward roots and spreading compost will involve continual bending and heavy lifting. And the most likely pain or injury will occur in the lower back region.
So not only should an ergonomic fork be suited to you but also to the task for which it is designed.
A quality design will place central importance on the shaft, which should eliminate the need to bend too far. Look for a fork with one of the following variables:
An extending / adjustable shaft.
An angle (or bend) along the length
An additional handle grip partway along the shaft.
An adjustable length of shaft
This is not only ideal for those who are tall or short but will also enable all users to customise the shovel to their height and the task.
A long enough shaft will prevent you from having to repeatedly bend, reducing the strain placed on the lower back. Likewise, if the shaft is too long, it will be harder to raise the fork off the ground.
An angle (or bend) in the shaft
Alternatively, the shaft should be angular or have a bend 2/3 way along its length. This will reduce debilitating forces to the spine when lifting a loaded fork off the ground as the user tends to remain more upright.
To counteract any difficulty in lifting a fork with a bent shaft, some ergonomic forks have an additional handle part way down the shaft allowing for a second point of contact. This allows any weight to be balanced equally in front of your body with both hands.
Other features of a suitable ergonomic fork include:
Cushioned, angled and roomy handle grips
These will provide the best grip and comfort, reducing the stress on your hands and wrists
Look for finger indentures for additional comfort. All these added details help moderate fatigue on the hands and wrists.
Lightweight materials
A quality wooden or fibreglass shaftrather than a heavy steel shaft is another factor to think about.
Lightweight and able to absorb shock and vibration, both are ideal materials to reduce stress and fatigue on the body.
Whatever your needs, it is worth searching for the right fork.
If your budget allows for the expense of buying forks with different functions then make sure you shop wisely. If, however, one multi-purpose shovel will have to suffice, then make sure that you are comfortable using it.