The Effectiveness of Pre-Employment Strength Testing for Manual Materials Handling Jobs *

Abstract

With the advent of both affirmative action programs for women and disabled individuals and the growing need for better occupational health and safety programs in heavy industry, it has become necessary to develop more objective pre-employment selection and employee placement tests. This paper reviews the eight years of research conducted on this subject by the University of Michigan, Human Performance and Safety Research Laboratory. Various human strength testing methodologies are described and critiqued. Population strength data are reviewed as they pertain to the problem of matching a person's physical capabilities to a job's physical demands.

The development and use of biomechanical strength models are reviewed, and their potential contributions and limitations are enumerated. Several major results of the use of such models for the design of manual materials handling tasks are presented. The transition from such biomechanical analyses to the development of a physical job evaluation methodology is presented. Two studies using this job evaluation methodology are then described.

The first study involved over 100 jobs requiring significant manual materials handling which were located in five different plants. The workers on these jobs were strength tested. Any low-back problems developed by these people were carefully documented over a one-year period. The results indicated that those jobs requiring high strength performance were associated with about an eight times higher incidence rate of low-back pain than the jobs having little strength requirement. Also, it was shown that those employees having a high strength capacity were significantly less prone (about 3X less) to low-back pain when required to lift heavy loads than their weaker peers.

The second study describes a larger on-going study of the same nature as the first. This study involves over 900 job evaluations. The jobs are located in six different plants. As people are transferred or hired into these jobs, their strengths are assessed by standardized tests, and a medical history is obtained. Both supervisor performance ratings and medical incident data are recorded while the person remains on the job. Correlations between the job demands relative to a person's strength test results and their performance and medical incident scores are reported as a measure of how effective strength testing could be in achieving a better employee/job match.