Exercise ECG: What It Shows That a Resting ECG Cannot

By Dr. Gabriel Grabowski, specialist in internal medicine and pulmonology

I see this often in my practice: someone feels comfortable while sitting, but notices breathlessness, chest discomfort or a racing heartbeat when walking uphill. A resting electrocardiogram, or ECG, may be unremarkable. That does not mean the symptoms should be dismissed. It means we may need to understand what happens when the body works harder.

An exercise ECG, also called a stress ECG, records the heart’s electrical activity during controlled physical effort. It can provide information that a short recording at rest cannot, although it is not the right test for every person or every symptom.

Why exercise can reveal a different picture

A resting ECG shows the heart’s rhythm and electrical activity while you are lying quietly. It can identify several abnormalities, but it captures only a brief period when the heart’s workload is relatively low.

During exercise, muscles need more oxygen. The heart usually responds by beating faster and pumping more blood. Blood pressure changes too. An exercise ECG allows me to observe these responses as the workload gradually increases and then decreases during recovery.

The important question is not simply whether you can pedal a bicycle or walk on a treadmill. It is whether your symptoms, ECG findings, heart rate and blood pressure change together in a way that helps explain your difficulties.

What the test can show

I assess several aspects together rather than interpreting one number or tracing in isolation:

• Symptoms during effort: When do breathlessness, chest pressure, dizziness or palpitations appear? Do they settle during recovery?
• Heart rhythm: Does exercise trigger extra beats or another rhythm disturbance? Does the heart rate rise appropriately and slow down afterwards?
• Blood pressure response: Systolic pressure—the upper number—normally rises with increasing effort. An unusually large rise, an inadequate rise or a fall may need further assessment.
• ECG changes under load: Certain changes can suggest that the heart muscle is not receiving enough blood during exertion.
• Exercise capacity: The workload reached helps put symptoms into context, although fitness, joint problems, medication and lung conditions all influence performance.

An exercise ECG does not directly show the coronary arteries or measure how severely they are narrowed. Changes suggesting reduced blood supply need to be interpreted alongside symptoms, medical history and other findings. Likewise, extra beats during exercise do not automatically mean a dangerous rhythm problem.

What happens during the appointment

Before testing, I review your symptoms, medical history and medicines, and assess whether exercise testing is suitable. Some acute illnesses or unstable heart conditions make it inappropriate until they have been assessed or treated.

Electrodes are attached to your chest, and a blood pressure cuff is placed on your arm. After baseline measurements, you exercise on a stationary bicycle or treadmill. The workload usually increases in stages while the ECG is monitored and blood pressure is checked regularly.

Tell the team promptly about discomfort, breathlessness, dizziness or unusual fatigue. The test can be stopped because of symptoms, significant ECG or blood pressure changes, or because you cannot comfortably continue. Monitoring continues during recovery, when useful changes may also occur.

Wear comfortable clothing and suitable shoes, and follow the practice’s preparation instructions. Do not stop heart or blood pressure medicines on your own: some affect the test, but any adjustment needs individual advice.

Understanding the result and the next step

A normal exercise ECG can be useful, but it does not rule out all coronary artery disease or explain every cause of exertional symptoms. If the workload achieved is too low, the result may be less informative. Some baseline ECG abnormalities also make interpretation difficult. Both false-positive and false-negative results are possible.

Depending on the clinical question, I may recommend another investigation instead of, or after, an exercise ECG. This might include longer-term rhythm monitoring, echocardiography, coronary CT or stress imaging. When breathlessness is the main concern, lung function testing or cardiopulmonary exercise testing may help distinguish possible causes. A standard exercise ECG alone cannot reliably separate heart, lung and fitness-related limitations.

New, recurring or worsening symptoms during ordinary activity deserve medical assessment, even if a previous resting ECG was normal. New or severe chest pressure, especially at rest or with marked breathlessness, sweating or fainting, requires urgent medical attention rather than waiting for a scheduled exercise test.

Consultations are possible at the three practices in Nürnberg, La Cala de Mijas and Estepona. Whether an exercise ECG is appropriate can be discussed after reviewing your symptoms and health history.

This article is general information and does not replace a personal medical consultation.