Stress Testing

Definition

Stress testing consists of a graded exercise test (GXT) that is performed to provide an objective evaluation of cardiorespiratory fitness and heart health.

Purpose




A doctor monitors a patient who is performing a stress test. Stress tests examine a person's cardiovascular capacity by measuring heart rate during increasingly strenuous exercise, typically on a treadmill.





A doctor monitors a patient who is performing a stress test. Stress tests examine a person's cardiovascular capacity by measuring heart rate during increasingly strenuous exercise, typically on a treadmill.
(Photographee.eu/Shutterstock.com)

Description

Stress testing can be performed in apparently healthy men or women. Alternatively, stress testing can also be executed in those individuals diagnosed with cardiovascular, pulmonary, or metabolic disease. Stress-testing procedures, monitoring, protocols, and indications for test termination will all vary depending on the health status of the test participant.

Resting heart rate and blood pressure should be obtained at baseline prior to commencing a stress test. Heart rate, blood pressure, and rating of perceived exertion (RPE) measures should be obtained throughout the stress test. Each of these measures should be recorded near the end of each stage of the stress test. ECG and expired gases can also be collected continuously during stress testing. All of these parameters should be assessed by the test administrator to ensure the response to exercise is normal. Additionally, the test administrator should also constantly monitor the test participant for physical appearance and possible appearance of adverse symptoms (e.g., shortness of breath, tachycardia).




Stress testing can be performed in apparently healthy men or women. Alternatively, stress testing can also be executed in those individuals diagnosed with cardiovascular, pulmonary, or metabolic disease.

Almost all stress-testing protocols are performed on either a treadmill or cycle ergometer. Popular treadmill and cycle ergometer stress-testing protocols include the Astrand, Bruce, Balke, Fox, Modified Balke, and Naughton. Each modality has advantages and disadvantages.

Approximately 75% of all stress testing is done on a treadmill. There are numerous advantages to this modality. Walking and running are familiar activities for most people. Treadmill exercise recruits substantial muscle mass and will increase the likelihood of obtaining maximal heart rate, blood pressure, and maximal oxygen uptake (VO2max). It is also easy to control the workload on the treadmill. Nevertheless, there are also a few drawbacks to using the treadmill. Higher-quality treadmills can be expensive. Additionally, some physiological measurements are more difficult to obtain on the treadmill, including exercise blood pressure and exercise ECG.

The cycle ergometer is an excellent alternative to the treadmill as a modality for stress testing and has many advantages. Cycle ergometers are less expensive and more portable as compared to treadmills. It can also be easier to obtain physiological measurements, such as exercise blood pressure and exercise ECG, on the cycle ergometer. The cycle ergometer is an excellent option for those individuals performing a stress test with orthopedic problems. Disadvantages to use of the cycle ergometer include cadence problems and premature fatigue due to localized fatigue in the quadriceps region. This latter point is one of the reasons that maximal heart rate and VO2max values tend to be 5%–10% lower on the cycler ergometer as compared to the treadmill.

Preparation

Prior to stress testing, individuals should undergo adequate preparticipation health screening and risk stratification to optimize safety. The purposes of the screening process are as follows: (1) to identify and exclude individuals with contraindications to exercise testing; (2) to identify the need for medical supervision of exercise tests; and (3) to identify individuals with other special needs. Two commonly used prescreening instruments include the Physical Activity Readiness Questionnaire (PAR-Q) and a Health History Questionnaire (HHQ). The PAR-Q evaluates one's health risks in a series of seven yes/no questions and encourages test-takers to seek medical attention prior to exercise testing if any question results in a “yes” response. Likewise, an HHQ can assist in the identification of existent diseases or medical conditions (e.g., cardiovascular disease, type 2 diabetes).

To minimize risk and obtain valid results, the test participant should be adequately prepared for the stress test. Accordingly, it is recommended that the following pretesting instructions be communicated to the test participant in advance of the appointment:

KEY TERMS
Angina—
Chest pain, pressure, or discomfort that occurs if a region of the heart muscle has an inadequate supply of oxygenated blood. Angina symptoms may also include pain in the shoulders, arms, neck, jaw, or back. Angina symptoms can also mimic indigestion.
Cardiorespiratory fitness—
The highest rate at which oxygen can be taken up and consumed by the body during intense exercise, typically determined by maximal oxygen uptake, or VO2max.
Cardiovascular disease—
A class of diseases that involve either the heart or blood vessels; the most common form is coronary artery disease.
Dyslipidemia—
Abnormal amount of lipids (e.g., triglycerides, cholesterol) in the blood.
Health History Questionnaire (HHQ)—
A screening instrument to provide insight into an individual's health prior to commencing a fitness program.
Hypertension—
High blood pressure; systolic blood pressure greater than or equal to 140 mmHg, and diastolic blood pressure greaterthan or equal to 90 mmHg.
Meta-analysis—
A statistical analysis that combines the results from numerous scientific studies.
Physical Activity Readiness Questionnaire (PARQ)—
A seven-question screening instrument designed to identify the small number of adults for whom physical activity may be inappropriate or those who should have medical advice concerning the type of activity most suitable for them.
Risk factors—
Physiological parameters that influence the progression of disease.
Risk stratification—
A preexercise screening process that identifies individuals with a heightened risk of exercise-related complications.
Shortness of breath (SOB)—
Difficulty in breathing.
Tachycardia—
Rapid heart rate of greater than 100 beats per minute.
Type 2 diabetes—
Long-term metabolic disorder characterized by high blood sugar, insulin resistance, and relative lack of insulin.

Aftercare

Stress testing typically continues until the participant reaches voluntary maximal exertion. Test administrators, however, must be vigilant for various indicators that may signify an adverse exercise response. The following are some common indications for terminating a stress test:

After the stress test has concluded, monitoring the heart rate, blood pressure, and ECG should continue for at least five minutes to ensure a gradual return to baseline values.

Risks

Risk stratification of an individual into categories of low, moderate, or high prior to stress testing provides insight into the degree of medical supervision required. The presence of positive cardiovascular disease risk factors provides a framework for riskstratifying individuals. The overall number of positive risk factors should be totaled. In the event no information is available for a specific positive cardiovascular disease risk factor, it has been recommended to assume the worst-case scenario and count the risk factor. Participants with positive risk factors for cardiovascular disease are at increased risk for ultimately developing cardiovascular disease and/or experiencing a stress-testing-related cardiac event. Positive risk factors are elements that contribute toward developing a disease. Similarly, individuals with known signs and/or symptoms of cardiovascular, pulmonary, and/or metabolic disease are at increased risk of an exerciserelated cardiac event or other complication.

After the preparticipation health screening process it is possible to risk-stratify individuals into one of three classifications (low, moderate, or high). It is recommended that individuals who are risk stratified into either the moderate- or high-risk category have physician supervision of the stress test. The criteria for low, moderate, and high risk are as follows:

Results

Stress testing yields many important results. Arguably, the most important is that stress testing provides an accurate assessment of cardiorespiratory fitness. Indeed, cardiorespiratory fitness has been coined the ultimate heart-health outcome.

The level of an individual's cardiorespiratory fitness revealed during a stress test is dependent on numerous variables including age, sex, race, training status, and genetics. Normative values for VO2max with specific reference to age and sex are available at the Cooper Institute website. Because low cardiorespiratory fitness is a powerful risk factor for CVD, it is important to assess how low is too low. It has been demonstrated that the highest relative risk of CVD exists for those individuals with cardiorespiratory fitness levels below the 20th percentile. Therefore, moving individuals out of the lowest 20th percentile of cardiorespiratory fitness is an important goal of prevention and rehabilitation exercise programs. In fact, it has been shown that the most substantial drop in CVD risk occurs when individuals move from the 20th to 30th percentile of cardiorespiratory fitness.

One of the very first studies to explore the connection between cardiorespiratory fitness and heart health was published in 1989 in a hallmark paper. It was reported that an inverse relationship existed between VO2max values and risk for CVD. It was also shown that this relationship held true for individuals with no other risk factors for CVD, one risk factor for CVD, and two or more CVD risk factors. In 2001, the question of whether cardiorespiratory fitness should be considered a separate risk factor for CVD, in addition to lack of physical activity, was addressed in a metaanalysis. The author noted that both increased cardiorespiratory fitness and increased physical activity were associated with decreased risk for CVD events. Moreover, it was also found that higher cardiorespiratory fitness levels yielded greater reductions in CVD risk compared to those imparted from increased physical activity levels. It was concluded that being unfit warrants consideration as a separate CVD risk factor, independent of physical inactivity and other traditional CVD risk factors. Perhaps the strongest case to support cardiorespiratory fitness as the ultimate heart-health outcome was made in a paper published in 2009. The author presented data to show that low cardiorespiratory fitness accounted for more overall deaths, including those from CVD, when compared to deaths that could be attributed to traditional risk factors, such as obesity, smoking, hypertension, dyslipidemia, and type 2 diabetes.

QUESTIONS TO ASK YOUR DOCTOR
  • Would I benefit from a stress test?
  • What risks are involved with stress testing?
  • Because stress testing involves ECG monitoring, can you explain what that entails?
  • Besides the ECG, what other monitoring is required during a stress test?
  • How long does a typical stress test last?
  • What should I do prior to a stress test?
  • Will I be tired after a stress test? How long will it take me to recover?

Resources

BOOKS

Heyward, Vivian H., and Ann L. Gibson. Advanced Fitness Assessment and Exercise Prescription. 7th ed. Champaign, IL: Human Kinetics, 2014.

Porcari, John P., Cedric X. Bryant, and Fabio Comana. Exercise Physiology. Philadelphia, PA: Davis, 2015.

PERIODICALS

Blair, Steve N., et al. “Physical Fitness and All-Cause Mortality: A Prospective Study of Healthy Men and Women.” Journal of the American Medical Association 262, no. 17 (November 1989): 2395–401.

Blair, Steve N. “Physical Inactivity: The Biggest Public Health Problem of the 21st Century.” British Journal of Sports Medicine 43, no. 1 (January 2009): 1–2.

Franklin, Barry A. “Fitness: The Ultimate Marker for Risk Stratification and Health Outcomes?” Preventive Cardiology 10, no. 1 (Winter 2007): 42–6.

Ross, Robert, et al. “Importance of Assessing Cardiorespiratory Fitness in Clinical Practice: A Case for Fitness as a Clinical Vital Sign: A Scientific Statement from the American Heart Association.” Circulation 134, no. 24 (December 13, 2016): e653–99.

Williams, Paul T. “Physical Fitness and Activity as Separate Heart Disease Risk Factors: A Meta-Analysis.” Medicine and Science in Sports and Exercise 33, no. 5 (May 2001): 754–61.

WEBSITES

Cooper Institute. “Study Shows Cardiorespiratory Fitness and LDL Are Predictors of Coronary Heart Disease.” Cooper Institute.org . https://www.cooperinstitute.org/pub/news.cfm?id=138 (accessed February 5, 2017).

Mayo Clinic Staff. “Stress Test.” Mayo Foundation for Medical Education and Research. http://www.mayoclinic.org/tests-procedures/stress-test/basics/definition/PRC-20019801.htm (accessed February 5, 2017).

ORGANIZATIONS

Cooper Institute, 12330 Preston Rd., Dallas, TX, 75230, (972) 341-3200, (800) 635-7050, Fax: (972) 341-3227, http://www.cooperinstitute.org/contact , http://www.cooperinstitute.org .

Mayo Clinic, 200 First St. SW, Rochester, MN, 55905, 1(507) 266-7890, http://www.mayoclinic.org/ .

Lance C. Dalleck, PhD

  This information is not a tool for self-diagnosis or a substitute for professional care.