Exercise tolerance testing
Peer reviewed by Dr Doug McKechnie, MRCGPLast updated by Dr Philippa Vincent, MRCGPLast updated 29 Apr 2025
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Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find the Exercise Tolerance Testing article more useful, or one of our other health articles.
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Synonyms: include exercise ECG testing, treadmill testing, exercise stress test
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What is exercise tolerance testing?
Exercise tolerance testing (ETT) is one method which is used to determine the presence of significant coronary heart disease. Chest pain is a common presentation both to general practitioners and to A&E departments.1 Often one of the differentials is cardiac chest pain; ruling this out in patients who might be otherwise well or who have few cardiac risk factors, can be difficult.
ETT has been quoted as having a sensitivity of 78% and a specificity of 70% in detecting coronary artery disease (CAD).2 Thus, a negative test may not necessarily be true and further testing or advice may be warranted. Diagnostic accuracy has previously been thought to be poor in women, possible due to smaller heart size.3 More recent studies suggest that the previous assumption of poor diagnostic accuracy (based on normal coronary angiograms following a positive stress test) may also be due to ischaemia with no obstructive coronary artery disease (INOCA), which is more common in women. INOCA occurs when there are structural or functional abnormalities of the coronary vasculature, such as microvascular dysfunction or coronary artery spasm. 4
ETT has been being superseded by cardiac imaging techniques, such as myocardial perfusion scans, in some centres. Even so, ETT can be valuable when performed in selected patients and the following criteria have been suggested:5
Ability to exercise.
Normal baseline 12-lead ECG.
No previous cardiac revascularisation.
Indications for exercise tolerance testing
Diagnosis of coronary heart disease (keeping in mind the high number of false positives and false negatives).
Assessment of 'fitness' in certain occupations and medical condition - for example, the police force and some cardiomyopathies.
Arrhythmias - ETT can help to record arrhythmias which are provoked by exercise (but only in those with non-life-threatening arrhythmias).
Most patients with suspected angina were traditionally referred for exercise ECG testing. Exercise ECG testing has a relatively high sensitivity but only moderate specificity for the diagnosis of CAD. A normal exercise test may reassure many patients but it does not exclude a diagnosis of CAD.6
The 2010 National Institute for Health and Care Excellence (NICE) guidance for patients presenting with chest pain recommends that exercise ECG should not be used to diagnose or exclude stable angina for people without known CAD.7
The NICE guidance also states that, for people with confirmed CAD (eg, previous myocardial infarction, revascularisation, previous angiography), non-invasive functional testing should be offered when there is uncertainty about whether chest pain is caused by myocardial ischaemia, and that exercise ECG may be used instead of functional imaging.7
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What the exercise tolerance test involves
ETT consists of exercising on a treadmill following a defined protocol, the Bruce protocol, over approximately 20 minutes. The test begins gently and gradually the level of intensity is increased through a combination of increased treadmill speed and incline.
Intensity of exercise is measured in metabolic equivalents (METs) where 1 MET is the amount of energy expended at rest or 3.5 ml oxygen per kilogram per minute.
The test is divided into seven stages of three minutes and there is also a less strenuous version called the modified Bruce.
ECG is recorded throughout and blood pressure measured intermittently.
ETT might be prematurely stopped for any of the following: development of chest pain, presence of ST elevation, very deep, 2 mm or more ST depression, arrhythmias, hypotension or if the patient becomes tired and is unable to continue. In addition, elevation of blood pressure to dangerous levels such as >250/115 mm Hg should also lead to termination of the test.
Beta-blockers and digoxin can interfere with the results so are usually stopped before the ETT.
Contra-indications to exercise tolerance testing
Chest pain at rest or at night.
Any condition where left ventricular output is reduced - for example, aortic stenosis or hypertrophic obstructive cardiomyopathy (HOCM).
Active systemic illness.
Abnormal baseline ECG (for example, bundle branch block patterns or left ventricular hypertrophy); these make interpretation of the ETT difficult.
Suspected or confirmed life-threatening arrhythmias.
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Interpreting the exercise tolerance test
ST elevation - usually this will be picked up straightaway and dealt with.
The patient is normally considered to have been adequately 'stressed' if they achieve 85% or more of their maximum heart rate (calculated as 220 - age in years for men and 210 - age for women). However, recent data suggest that using these criteria to terminate the test may lead to an underestimation of inducible ischaemia.8
At each stage each lead should be examined for:
Planar ST depression (this can be difficult to delineate from depression of the J point, which is the point where the QRS complex meets the ST wave).
'Flipping' of the T waves.
Arrhythmias.
Examination of all leads should continue into the recovery stage after the exercise stage of the test has been completed.
Complications of exercise tolerance testing
These are rare but can be fatal - for example, myocardial infarction, left ventricular rupture, ventricular fibrillation or ventricular tachycardia.
Following up an abnormal exercise tolerance test
Cardiologists will normally investigate further if an adequate ETT was undertaken and is abnormal.
If an inadequate test was performed, further non-invasive investigations may be indicated, such as myocardial perfusion scanning, cardiac MRI, or stress echocardiogram. Again these will be organised by cardiologists.
Further reading and references
- Vilcant V, Zeltser R; Treadmill Stress Testing
- Fitzgerald P, Goodacre SW, Cross E, et al; Cost-effectiveness of point-of-care biomarker assessment for suspected myocardial infarction: the randomized assessment of treatment using panel Assay of cardiac markers (RATPAC) trial. Acad Emerg Med. 2011 May;18(5):488-95. doi: 10.1111/j.1553-2712.2011.01068.x.
- Megnien JL, Simon A; Exercise tolerance test for predicting coronary heart disease in asymptomatic individuals: A review. Atherosclerosis. 2009 Aug;205(2):579-83. Epub 2008 Dec 31.
- Siegler JC, Rehman S, Bhumireddy GP, et al; The accuracy of the electrocardiogram during exercise stress test based on heart size. PLoS One. 2011;6(8):e23044. Epub 2011 Aug 17.
- Rethinking the Goal of Exercise Tolerance Testing: Identifying Ischemic Heart Disease, Whether Epicardial or Microvascular; Journal of the American College of Cardiology
- Miller TD; Stress testing: the case for the standard treadmill test. Curr Opin Cardiol. 2011 Sep;26(5):363-9.
- Management of stable angina; Scottish Intercollegiate Guidelines Network - SIGN (April 2018)
- Chest pain of recent onset; NICE Clinical Guideline (March 2010, updated Nov 2016)
- Jain M, Nkonde C, Lin BA, et al; 85% of maximal age-predicted heart rate is not a valid endpoint for exercise treadmill testing. J Nucl Cardiol. 2011 Dec;18(6):1026-35. Epub 2011 Sep 16.
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Article history
The information on this page is written and peer reviewed by qualified clinicians.
Next review due: 28 Apr 2028
29 Apr 2025 | Latest version

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