Pushing and pulling are common work activities in many work environments. Jobs may require pushing and pulling large and small items, levers, cables, boxes, carts, and more. Employers, physicians, and even some therapists have misunderstood the meaning of push and pull forces. For example, here are some of the typical myths being perpetuated out there:
If a job requires 50 lbs. of push force, you can determine whether applicants meet the job's demand by putting 50 lbs. in a crate and having them push the box across a countertop.
If you push a 300 lb. patient in a wheelchair, it requires 300 lbs. of push force.
If a patient has a 20 lb. restriction, they cannot push a utility cart with more than 20 lbs. on it.
The Truth of the Matter
Push and pull force is more complicated than most people realize. When doing a functional job analysis or pre-work screen, the amount of force needed to push or pull an object must be measured by a force gauge and is influenced by the following factors;
Size/shape of the object
Weight of the object
The location of the object
Is the object on wheels? Larger diameter wheels make the push/pull easier than smaller diameter wheels. A
Are the wheels/bearings properly maintained, or are they all gummed up and sticking?
Is the object on tile, carpet, or outside on rough terrain?
Are you pushing on level surfaces, up a ramp or incline, down a ramp, or on a declined terrain?
Are there transition points that the object must be pushed/pulled over?
Are there easy places to grip the object for pushing or pulling?
Our bodies can typically generate more pulling force than pushing force. However, when we pull objects, we twist our bodies to see where we are going. Therefore, in back safety programs, patients are recommended to push rather than pull. Pushing tends to use leg strength to move the object, and it is easier to maintain the lumbar lordosis and avoid twisting.
Measuring Push/Pull Forces
When measuring push or pull force, you must use a force gauge. The technique requires positioning the gauge (force) parallel to the ground and applying a steady push or pull. You only want to record the actual force required to get the object moving. Each job must be evaluated based on the conditions, the equipment, and the objects being pushed or pulled in that specific job. Because there are so many factors that influence the measurement of force, a push/pull gauge is the only means to measure accurately.
Here are some examples of push/pull forces required to move an object. NOTE: These are examples only and should not be substituted for actual measurements under actual work conditions.
Example #1: A utility cart with 4” wheels in good condition and holding 141 lbs. of weight required between 7 to 10 pounds of force to get the cart moving. Once it was moving, only 5 pounds of force was required to keep the cart in motion.
Example #2: A manual pallet jack was loaded with various weights and the push/pull force to initiate movement of the pallet jack was as follows, based on the weight load:
240# required 10# of force
640# required 26# of force
960# required 33# of force
1280# required 54# of force
1600# required 71# of force
2000# required 100# of force
Example #3: Pushing a wire basket holding 50 pounds of weight across a smooth countertop required 10 lbs. of force. Pushing the same wire basket weight load over a hard surface floor required 13 lbs. of force. Each job must be evaluated based on the conditions, the equipment, and the objects being pushed or pulled in that specific job. Because there are so many factors that influence the measurement of force, a push/pull gauge is the only means to accurately measure. This force is then used as the critical demand when doing a job match in an FCE or in PWS testing.
If a job description indicates the need to push 300# a distance of 20 feet, job matching cannot be completed with this limited information. Doing a job-specific push activity at the end of your FCE will provide additional information, but qualify any conclusions with the specifics of how you simulated the activity and what equipment was used. The variables in your clinic may not reflect what is encountered at the worksite. Document the client's push/pull abilities, explain any job simulation testing that was done, and make the case that the job description does not include the measured force required to move 300#. Information should be confirmed/validated by the employer before a final recommendation can be made related to return to work.