3:46 am January 19, 2017

Demystifying Push/Pull Force

Source: Steve McKenney, PT

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, he or she 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
  • 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 or 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 tend to 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 to 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 accurately measure.

For your job‘s specific needs and employee matching, ask any of our qualified WorkWell therapists for more detailed information.

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