Study Participants
The data presented in this case study were collected from 147 individuals working in physically demanding jobs including electricians, construction and maintenance workers, auto mechanics, and linemen. An analysis of the tasks performed in these jobs showed that a number of them required a substantial amount of strength to perform. Here are some examples of physically demanding tasks performed in some of these jobs.
Physical Strength Measures
Two measures of strength were gathered from each participant. These included grip and arm strength. A piece of equipment known as the Jackson Evaluation System (JES) was used to collect the strength data. The JES can be configured to measure the strength of a number of muscle groups. In this study, grip strength and arm strength were measured. For each of the tests, the participant was asked to exert as much force as they could for a period of 2 seconds. The equipment then measured the maximum force exerted in pounds (lbs.). Since there is little to no movement along any joints, these measures are often referred to as isometric strength measures. To increase the accuracy of the measure, participants were asked to perform each test twice. The two scores were then averaged together for each of the two strength measures (grip and arm).
Job Performance
Two separate measures of job performance are presented in this case study. First, the supervisors for each of the 147 study participants were asked to rate how well their employee(s) perform on the physical aspects of their jobs using a 60-point scale. Higher numbers indicate better performance on the physically demanding aspects of the job.
Second, two work simulations were developed by using information collected from an analysis of the jobs as well as observations and measurements of individuals performing each of the jobs studied. The simulations required that the participant exert force on a simulated wrench while assuming a standing and a kneeling position. The scores on each of the simulations were standardized and summed together to form one single measure. Larger scores indicate better performance on the work simulations.