Short answer: an electrocardiogram, or ECG, records the heart’s electrical activity through electrodes placed on the skin. It can show heart rate, rhythm and electrical patterns that may suggest an arrhythmia or underlying heart condition.
Athlete ECGs require athlete-specific interpretation. Endurance and intensive training can produce normal electrical adaptations that may be mislabelled as disease by a generic computer report. An ECG is useful, but it does not show every heart problem and cannot provide a blanket “safe to train” certificate.
Key takeaway: the value of an athlete ECG depends on why it was performed, the quality of the recording and interpretation by a clinician familiar with athletic adaptation.
Table of contents
- What is an ECG?
- What an ECG can show
- What an ECG cannot rule out
- Why athlete ECGs are different
- Common training-related findings
- Findings that may need investigation
- When an athlete may need an ECG
- Resting ECG, Holter, stress ECG or echocardiogram?
- Enhanced-athlete considerations
- How to prepare
- Frequently asked questions
- References
What is an ECG?
A standard resting 12-lead ECG is a quick, non-invasive test. Adhesive electrodes are placed on the chest and limbs while the person lies still. The machine records electrical signals from different angles.
The trace contains waves and intervals that describe how an electrical impulse begins and travels through the heart. The test does not send electricity into the body.
What an ECG can show
- heart rate and rhythm at the time of recording;
- atrial fibrillation and some other arrhythmias;
- conduction delays or heart block;
- electrical patterns that may suggest chamber enlargement;
- patterns associated with some cardiomyopathies or inherited electrical conditions;
- changes that may occur with reduced blood supply or a previous myocardial infarction; and
- clues that justify echocardiography, exercise testing, monitoring or specialist review.
The automated interpretation printed by the machine is a prompt, not a final diagnosis. Australian acute coronary syndrome guidance notes that computer algorithms vary and can misclassify findings, so clinical interpretation remains essential.
What an ECG cannot rule out
A normal resting ECG does not exclude:
- coronary artery plaque;
- high blood pressure;
- intermittent arrhythmias that did not occur during the recording;
- every cardiomyopathy or structural abnormality;
- heart-valve disease;
- adverse cholesterol or ApoB;
- exercise-induced electrical problems; or
- future cardiovascular events.
An ECG is one layer of assessment. Symptoms, family history, examination, blood pressure, blood tests and imaging may answer different questions.
Why athlete ECGs are different
Repeated intensive training can alter autonomic tone and cardiac loading. These physiological adaptations can change the ECG without representing disease.
The International Criteria for Electrocardiographic Interpretation in Athletes were developed to distinguish common training-related patterns from findings that should trigger further evaluation. They are intended for trained clinicians and must be applied with age, ethnicity, symptoms, family history and sport in mind.
The criteria were designed principally around asymptomatic athletes aged 12 to 35. Older athletes have a different risk profile, including a greater probability of coronary artery disease, and need age-appropriate assessment.
Common training-related findings
Depending on the athlete and clinical context, training-related patterns may include sinus bradycardia, first-degree atrioventricular block, Mobitz type I second-degree block, incomplete right bundle branch block, early repolarisation and isolated voltage criteria for left ventricular hypertrophy.
That list is not a self-interpretation guide. Lead placement errors and combinations of findings can change the meaning. A consumer should not clear an abnormal report by matching one phrase to an online table.
Findings that may need investigation
International criteria classify patterns such as T-wave inversion in specified territories, ST-segment depression, pathological Q waves, complete left bundle branch block, ventricular pre-excitation, prolonged QT and certain ventricular arrhythmias as abnormal or potentially concerning.
Some isolated findings are described as borderline and may not require investigation on their own in an asymptomatic athlete. Two or more borderline findings generally change the assessment. The clinician decides the next test based on the complete pattern and history.
Further investigation may include an echocardiogram, exercise test, Holter monitor, cardiac MRI, blood tests or review by a sports cardiologist. An abnormal ECG is not automatically a diagnosis, and a normal first follow-up test may not always end surveillance.
When an athlete may need an ECG
A clinician may recommend an ECG for:
- exertional chest discomfort;
- unexplained fainting or near-fainting;
- recurrent palpitations or an irregular pulse;
- unexplained breathlessness or loss of exercise capacity;
- a family history of premature sudden cardiac death or inherited heart disease;
- an abnormal examination or blood pressure finding;
- pre-participation screening in selected organised sport settings;
- monitoring a known heart condition or a medicine that affects rhythm; or
- a wider clinician-led assessment of elevated cardiovascular risk.
The Australasian College of Sport and Exercise Physicians and European sports-cardiology guidance support ECG-inclusive pre-participation screening for elite athletes when appropriate expertise and follow-up are available. Screening policy is not identical for every recreational athlete.
Resting ECG, Holter, stress ECG or echocardiogram?
| Test | Main question | Important limitation |
|---|---|---|
| Resting 12-lead ECG | What is the heart’s electrical pattern now? | Brief snapshot |
| Holter or event monitor | Does a rhythm problem occur over hours, days or weeks? | May still miss infrequent events |
| Exercise ECG | What happens to rate, rhythm and electrical pattern with exertion? | Does not directly image structure |
| Echocardiogram | How are chambers, valves and pumping function structured? | Not a continuous rhythm test |
The right test depends on the symptom and the suspected condition. The next article in this series explains echocardiograms for athletes.
Enhanced-athlete considerations
Supraphysiological anabolic-androgenic steroid exposure is associated with adverse cardiovascular changes in observational studies, including altered heart structure and function. A resting ECG may contribute to an assessment, but it cannot prove that an enhanced athlete is free from harm.
A normal ECG does not cancel hypertension, adverse lipids, erythrocytosis, sleep apnoea, stimulant exposure or structural remodelling. These require their own measurements and, where indicated, imaging.
Be honest with the clinician about AAS, growth hormone, thyroid hormone, clenbuterol, stimulants and other drugs. That information can change how palpitations, QT interval, blood pressure and test selection are interpreted. See the complete heart-health guide for enhanced athletes.
How to prepare for a resting ECG
- Follow the clinic’s instructions.
- Bring a current list of medicines, supplements and performance-enhancing drugs.
- Report symptoms, when they occur and any family history.
- Avoid applying oily lotion to the chest immediately beforehand.
- Tell staff about skin sensitivity, implants or relevant medical conditions.
- Ask for the trace to be reviewed in athlete context if you train intensively.
Do not delay emergency assessment to arrange a routine ECG. Chest pressure, collapse during exercise, severe breathlessness or a sustained dangerous-feeling rhythm requires urgent care. In Australia, call Triple Zero (000) for an emergency.
Frequently asked questions
What does an ECG test?
It records the heart’s electrical activity, including rate, rhythm and conduction patterns.
Is an ECG painful?
No. It is non-invasive, although removing adhesive electrodes can briefly pull on skin or hair.
Why can an athlete ECG look abnormal?
Training can produce normal electrical adaptations, so athlete-specific interpretation is important.
Can an ECG detect blocked arteries?
It may show changes associated with reduced blood flow, but a normal resting ECG does not exclude coronary plaque or narrowing.
Does a normal ECG mean my heart is healthy?
Not completely. It cannot rule out every structural, coronary or intermittent rhythm problem.
Can a smart watch replace a 12-lead ECG?
No. Wearables can capture useful rhythm information, but they provide fewer leads and are not a substitute for clinical assessment.
What is the difference between an ECG and an echocardiogram?
An ECG records electrical activity; an echocardiogram uses ultrasound to examine structure and function.
Should enhanced athletes get an ECG?
Testing should be individualised according to symptoms, history, exposure and clinician assessment. An ECG may be one useful layer, not a complete safety screen.
Who should interpret an athlete ECG?
Ideally, a clinician trained in contemporary athlete ECG criteria and able to arrange follow-up testing.
References and further reading
- International Criteria for Electrocardiographic Interpretation in Athletes
- Heart Foundation: medical tests for heart disease
- Australian clinical guideline for acute coronary syndromes
This article provides general education and cannot interpret an individual ECG. Seek assessment from a qualified health professional who understands athlete-specific findings.