Metabolic Endurance Testing

The federal court's increased support of functional capacity evaluation as a return to work tool (Paul James v Goodyear Tire and Rubber; Leger v Chicago Tribune Company) underscores the need for occupational therapists to understand the terminology, origin, methods and strengths of metabolic endurance testing. Used widely in functional capacity evaluation, post-offer testing and disability evaluation, the MET test is often the cross-examination point of attack for an attorney addressing the validity of a return-to-work evaluation.

"MET testing" combines the concept of MET (meaning "metabolic equivalent of task" or "metabolic equivalent") with the concept of estimating an individual's capacity for work based on a series of controlled exercise tests.

The origin of modern MET testing is attributed to Nagle, Balke and Naughton's Gradational Step Testing for Assessing Work Capacity, published in the Journal of Applied Physiology in 1965. McArdle, Katch and Katch's research then helped determine the units of energy required to perform a wide range of ADL and work tasks (Exercise Physiology Energy and Human Nutrition, Lippencott, Williams and Wikins). Taken together, these provide tools to estimate an individual's short-term ability to engage in tasks and activities requiring relatively easily quantifiable units of energy.

An OT's use of MET testing is often focused on the broader question of full-day work capacity. The question presented is, "does this individual have the capacity to safely engage in a particular job, with a wide array of work demands, over the course of a full work day?" The full-work-day question requires the use of tools that convert short-term tolerance for exertion into an estimate of full-day capacity. This estimate of full-day work capacity must then be matched to an estimate of the MET requirements of a dynamic job.

An estimate of the energy requirement of a particular class of jobs can be obtained by reference to the U.S. Department of Labor's (DOL) Dictionary of Occupational Titles (DOT) and to the DOL's Physical Demand Characteristics of Work System. This system categorizes the strength demands of jobs into sedentary, light, medium, heavy and very heavy. The strength requirement of a job classification is determined by consideration of the lifting, carrying, pushing, pulling and awkward postures he uses.

During the 1970s a useful crosswalk between the DOL strength demand of a job and the MET requirement of an individual to successfully carry out the duties of the job was developed at Rancho Los Amigos Hospital in Downey, CA. That work resulted in the Physical Demand Characteristics of Work Chart, published by Leonard Matheson in 1979. The chart recognizes the relationship between the forecasted full-day MET ability of an individual as determined by a standardized MET test and NIOSH's estimate that an individual working at 55 percent of target heart rate can maintain 35 percent of his forecasted MET ability over an 8-hour day.

The key to estimating the individual's MET ability is the standardized metabolic endurance test. It is imperative that the OT using MET testing as a clinical tool understand at great depth the process of testing. Resources for this include the American College of Sports Medicine's Guidelines for Exercise Testing and Prescription and Testing and Y's Way to Physical Fitness by Golding, Myers and Sinnings.

The task for the clinician is to incorporate MET testing in the battery of standardized tests without raising a validity challenge. This can be done by placing the MET test within the safety section of the battery. The clinician must perform each test with some level of safety-related tools. MET testing for cardiac endurance, gait analysis, whole-body motion and balance fits under the safety umbrella.

Roy Matheson is founder and president of Roy Matheson and Associates, Inc., a leading provider of training and certification for therapists performing FCEs, post-offer testing and ergonomic evaluation services. He serves on the board of directors of the MTM Association for Standards and Research. Reach him at

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