Methods and limitations of assessing functional work capacity objectively

Abstract

This paper examined the methods and issues of assessing objectively the functional capacity of workers. The primary emphasis was on aerobic capacity (VO2max ) and repetitive lifting. While the direct measurement of expired gases during exhausting exercise is the most valid method of assessing the VO2max of workers, it is rarely done outside research or medical settings. The methods more commonly used are: maximal exercise tests; submaximal exercise tests; and non-exercise tests. Maximal tests are accurate, but require medical monitoring when testing workers at medical risk. Submaximal tests are less accurate, but are safer and faster than a maximal test. Submaximal tests use heart rate response to submaximal power output to estimate VO2max ; thus, any factor that alters heart rate response reduces the accuracy of the test. Non-exercise tests are as accurate as sub maximal tests, but require a self-report rating. The physiological criteria used to help define the recommended repetitive lift loads of the revised NIOSH equation included baseline aerobic capacity and energy expenditure values. While the goal is to reduce the risk of injury, the baseline aerobic capacity (≈ 25 ml/kg/min) and energy expenditure levels are so low (≤3.5 METs) that they may have an adverse effect on public health. Normative VO2max data on industrial cohorts suggest that 44% of male and 79% of female industrial workers are at a health risk of low aerobic fitness. Data are presented that suggests that repetitive lifting tasks are more of a function of strength and fat-free weight than aerobic capacity. While aerobic capacity, strength, and fat-free weight are objective methods to assess functional capacity, worker motivation and reaction to chronic pain can affect test results.