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Clinical Applications

Exercise Testing: Diagnosis, Function, and Prognostic Applications in Health Fitness

Humphrey, Reed Ph.D., P.T., FACSM

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ACSM's Health & Fitness Journal: November 2006 - Volume 10 - Issue 6 - p 36-37
doi: 10.1249/01.FIT.0000252518.52241.70
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In Brief

In 1977, I was hired to supervise graded exercise stress testing at a hospital in the Midwest. One of the controversies of the day was the value of exercise testing as a diagnostic tool for cardiovascular disease. Some 30 years and ∼15,000 tests later, it seemed a bit odd to me to be asked to debate this question at a recent conference, given the value I had come to appreciate about exercise testing in the context of primary and secondary prevention. To discuss diagnosis as a singular application seemed too narrow a focus at a gathering of health/fitness professionals weighing the value of exercise testing. It was a reminder to me that aside from the consensus that exercise is indeed good for virtually everyone, the work to appreciate the many applicable dimensions of the exercise test-diagnostic, functional, and prognostic-is perpetual.

The intersection of the exercise test as an evaluation to assist in the diagnosis of underlying cardiovascular disease and its utility as a functional measure of fitness has been a road well traveled. Much as a drug can be prescribed for applications beyond its original intent, so is the exercise test. Moreover, and perhaps less appreciated, the term diagnosis when associated with exercise testing has similar parallel meanings. In medicine, exercise testing is an assessment option in the diagnosis of cardiovascular disease. In that regard, exercise testing has limited value, in a strict sense. Many studies have demonstrated these limitations through a focus on the suboptimal interpretative value of electrocardiography, and as a result, exercise testing is frequently combined with another evaluation such as echocardiography or a radionuclide study to enhance diagnostic sensitivity. Nonelectrocardiographic variables, such as chronotropic incompetence and recovery heart rate, can be used to enhance the diagnostic value of the exercise test (1).

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That said, diagnosis does have parallel interpretation in the context of exercise testing and subsequent training. For example, a physical therapist cannot make a medical diagnosis about the determination of cardiovascular disease within their scope of practice, but can make a physical therapy diagnosis using the exercise test to determine the impairments amenable to treatment, such as impaired aerobic capacity or endurance. This terminology has been well described in the physical therapy literature (2). Exercise physiologists and health/fitness instructors would make similar determinations about the degree of impaired fitness. While seemingly a semantic exercise, it is helpful to better understand the context in which these terms are appropriately used across practice settings. Functionally, an appropriately conducted test yields important information about fitness, tolerance to specific levels of physical stress, and the cardiovascular responses (heart rate and blood pressure) to incremental physical effort. For patients with known cardiovascular, metabolic, or pulmonary disease, an upper safe limit of exercise may be identified with the participation of the client's physician. Exercise tests provide for goals to be reasonably set and provide a baseline for later comparison.

For participation in health/fitness programs, exercise testing has at least this dual application: to "clear" clients for participation, in essence a diagnostic application, and as a functional measure of fitness. That said, the application of exercise testing in the context of health and fitness is likewise often a challenge in the screening of new clients. Although ACSM guidelines are readily available to help steer a decision about the necessity of testing in the clearance of clients for exercise (3), professional judgment is still warranted for clients that don't clearly fit into a classification. Moreover, the need for a medical evaluation and an exercise test often is an unanticipated expense and potential barrier to participation, particularly for the asymptomatic but nonetheless at-risk client, according to ACSM guidelines. The discussion of the prognostic contributions of the exercise test may help clients better understand the value of the test. There is a prognostic "wow" factor that has emerged in the exercise testing literature in recent years that provides substantial weight to the value of exercise testing. Aside from gathering the important perceptual (rating of perceived exertion)-physiological (heart rate, workload) correlates, so helpful in exercise prescription, many studies have clearly shown that the exercise test can be used to predict cardiovascular risk (4-6). Froelicher (7) summarizes these studies nicely in a compelling editorial about the importance of combining risk factor assessment and exercise testing to identify long-term cardiovascular risk. In addition, in recent years, research has demonstrated the relationship of peak exercise capacity and longevity, where studies have shown a definitive link between increased fitness and decreased mortality, in at least one study, upward of 20% per MET increase in exercise capacity (8).

In summary, health/fitness professionals might consider the value of exercise testing on a continuum that stretches from diagnosis (and clearance for exercise) to function (for exercise prescription) to prognosis (perhaps to motivate clients with regard to risk factor modification). A thorough understanding of the many applications of the exercise test should help to make the road to optimal health and fitness a bit less difficult to navigate.

References

1. Lauer M., E. Sivarajan Froelicher, M. Williams, et al. Exercise Testing in Asymptomatic Adults. A statement for professionals from the American Heart Association Council on clinical cardiology, Subcommittee on Exercise, Cardiac Rehabilitation, and Prevention. Circulation 2005;112:771-776.
2. Guide to Physical Therapist Practice. 2nd ed. American Physical Therapy Association. Physical Therapy. January 2001;81(1):44-46.
3. ACSM's Guidelines for Exercise Testing and Prescription. 7th ed. American College of Sports Medicine. Lippincott Williams & Wilkins, Baltimore, 2005.
4. Gibbons L.W., T.L. Mitchell, M. Wei, et al. Maximal exercise testing as a predictor of risk for mortality from coronary heart disease in asymptomatic men. American Journal of Cardiology 2000;86:53-58.
5. Balady G.J., M.G. Larson, R.S. Vasan, et al. Usefulness of exercise testing in the prediction of coronary disease risk among asymptomatic persons as a function of the Framingham risk score. Circulation 2004;10:1920-1925.
6. Erikssen G., J. Bodegard, J.V. Bjornholt, et al. Exercise testing of healthy men in a new perspective: from diagnosis to prognosis. European Heart Journal 2004;25:978-986.
7. Froelicher V. Screening with the exercise test: time for a guideline change? European Heart Journal 2005;26(14):1353-1354. Epub April 26, 2005.
8. Myers J., A. Kaykha, S. George, et al. Fitness versus physical activity patterns in predicting mortality in men. American Journal of Medicine 2004;117:912-918.
© 2006 American College of Sports Medicine