Force is the mechanical effort that is required to carry out a movement or to prevent a movement. It is easy to think of the force required to lift a heavy object, but more difficult to remember the high level of force required to hold an item in place, or the increase of internal force if you hold a relatively light item out from your body. We refer to this as internal force vs external force.
External forces are more easily measured and tend to be the forefront of recommendations to reduce injury. External forces are the loads exerted on or by the surface of the body, such as:
- Handling objects
Internal force is much more difficult to assess and measure. Internal force refers to the tension generated within the muscles, tendons, ligaments and body tissues, as an external force is applied.
There have been many studies that demonstrate that if you put a high amount of force through the tips of your fingers, such as when holding a metal beam in place to be cut, the pressure in the carpal tunnel increases to a point where there will be damage to the nerves and tissue fibres. Unlike repetition, damage can occur with very short exposure times if the force is excessive.
Management of Force
It can be difficult to manage the risk of excessive force. A few tips include:
- Don’t wear bulky gloves as they can increase the required grip force by as much as 30% – try to get gloves that are slim, not bulky, and provide tactile feedback
- Carry all loads close to your body
- If you can use a tool to reduce the force required – use it
- Don’t use your hands to hold objects in place if you can use a vice instead
Hope this helps shed some light on the Risk Factor of Force. Check out our other posts in the Ergonomic Series.