Two people running outdoors

Measuring How Your Heart Responds to Physical Exercise

The what, why, and how of the stress test for runners.

Two people running outdoors on a sunny day

What Is A Stress Test?

A stress test, also called an exercise stress test, shows doctors how well your heart works during intense physical activity. It gives a more thorough picture of your cardiac health than tests given while you’re at rest.

You’ll typically run or walk on an incline treadmill, or ride a stationary bike. You’ll have 12 leads connected from an electrocardiogram machine to your skin at precise points on your torso. These read your pulse and create a picture of your heart’s electrical activity from many angles.

A stress test can accomplish the following:

1. Diagnose coronary artery disease.

2. Diagnose heart rhythm irregularities (arrhythmias, including atrial fibrillation).

3. Give a doctor guidance on a treatment plan that’s in progress.

A stress test can be expanded to test fitness:
If you’re a competitive athlete, your coach or sports physiologist may ask for a VO2 Max test to be included in your stress test. This is to evaluate your overall aerobic fitness level. In this version of the test, you’ll be fitted with a mask that measures the carbon dioxide content of all the air you exhale. Instruments will calculate how much oxygen you’re able to process during peak activity, measured in milliliters of oxygen per kilogram of bodyweight per minute.

When Do You Need A Stress Test?

Doctors are likely to prescribe stress tests under the following circumstances:

1. If you’ve been sedentary, and would like to start exercising seriously.

2. At routine intervals, after you’ve reached a particular age.

3. If you’ve shown symptoms of any heart problems.

4. If you’re a competitive athlete, and your progress is being monitored scientifically (in this case the test will likely be ordered by a coach or sports physiologist rather than a doctor).

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What Does A Stress Test Involve?

You’ll be given instructions on pre-test preparations, which may include modifications to any medications you take. You’ll probably be asked to avoid caffein for the day. You may be asked to not eat for a certain period right before the test.

You’ll have a dozen electrodes attached with adhesive patches to various spots on your torso. You’ll have a standard blood pressure cuff attached to your upper arm. If they’re testing oxygen uptake, you’ll also be fitted with a mask that captures all of your exhaled air and sends it by tube to a machine.

The test itself will usually be conducted on an incline treadmill or a stationary bike. Ideally, you want to use an exercise that’s closest to your sport, which means that runners should ask for a treadmill. The technician will have you follow a precise sequence of warmup and gradual increase in intensity, while watching the ECG results in real time. You may be asked to go all the way to your maximum heart rate. This is an extreme intensity level; you may not get there without enthusiastic encouragement from the technician. And you’ll be happy when the test is over. If there are irregularities, or if you feel chest pain or dizziness, the test may be stopped early.


Results should be available immediately to discuss with you doctor. If the test was precautionary and results are normal, you may be done. If the test was for diagnosing symptoms or guiding medical treatment, you may need further testing. If the test was for evaluating athletic fitness, you’ll be given data that you can share with your coach.

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