People push and pull things all day long – doors, wheelchairs, buttons, chairs, bins, and boxes. We rarely think about the best way to push something. Ergonomists, asked about the risks associated with pushing a load, will usually focus on the force required, the hand height, the type of grip required, pushing frequency, and the distance the load has to travel. (And rightly so – these factors have been shown to have the greatest effect on injury risk, and often require re-design.) In this article, I want to focus on pushing method – things that we can do to make a pushing “task” easier. To demonstrate the differences between methods, I’m reporting my own strength values.
1. Push forward. You will always (ALWAYS, in capitals) have more strength pushing straight forward than sideways, up, or back. If you can safely position yourself so that you can push forward instead of sideways or on some weird angle, do it! (If you are pushing downward, you can use your body weight which is also easier.)
My push strength forward with two hands, as shown: 50 lbs
2. Use two hands. Not rocket science: two hands are stronger than one. If you can free up a second hand to help, you’ll make the task easier. For example, if you usually hold the two handles of a cutting tool and pull them together to cut something (pipe, branches, wire), each hand exerts an equal amount of force. If you are able to brace one handle in a vice, you can use both hands to push the other handle – half as much pushing effort for each of your hands! Even if you must push sideways, for example to slide a box along a roller conveyor, two hands are better than one – one hand can pull while the other hand pushes.
My push strength forward with one hand: 32 lbs
My push strength sideways (with one hand): 10 lbs
3. Make a stronger base. Keep your feet shoulder width apart, ideally with one slightly ahead of the other, as shown in the top photo. This allows your feet better traction. Not convinced that this matters? Try this: Stand behind your sofa (or a heavy cart, or box). With your feet together (as shown at right), try to push the sofa a few inches away from you. On a 10-point scale, how difficult was that? (Perhaps 5-6?) Now repeat the push with your feet shoulder width apart, one foot a bit forward of the other. How difficult was it, in comparison? (Perhaps only 2-3?)
My push strength with feet together: 25 lbs
4. Palm it, or get a good grip. Pushing with the palm of your hand, such as when you open a push door, is easiest. If you have to grip an object while you push or pull, you’ll need the muscles of your hands, as well as your arms, back, and legs. When pushing objects that require control, such as wheelchairs, carts, or drills, make sure that your hand grips the object firmly. Use grippy gloves, or cover the handles with rubberized coating, if the object is slippery. If you are pushing an unfamiliar object, plan your grip carefully to ensure that it will be secure and comfortable.
I hope that I’ve nudged (pushed?) you to think twice before you push something!