When job redesign is not an option, select workers who have the physical capacity to meet the demands of the job. While job redesign is an effective ergonomic strategy, it is not always possible. Many products and containers are already designed at their optimal weight and size. When the demands of a materials lifting task cannot be engineered out of the task, the second option is to select workers who are able to meet the demands of the job. Research has demonstrated that isometric strength tests are an effective measure of a prospective worker's ability to perform manual materials handling tasks.
Isometric strength is the maximum force that a muscle group can exert without movement.
Tests of isometric strength are easy to perform since they require only a single maximal contraction. Isometric tests are much safer than other kinds of tests such as those that ask workers to lift increasingly heavy weights to establish a worker's maximal level of strength. This is because isometric tests do not ask workers to lift weights, only exert force. If a worker can only exert 25 lbs. of force, that worker's score is 25lbs. On the other hand, if a worker is very physically capable, he or she may exert 125 lbs. or more of force on the same test.