What is a Heart Rate Drift test?

A heart rate drift test is a simple and cheap way to determine your aerobic threshold. It is a one-hour test where you run outdoors at a steady heart and record your pace. More inforation about the specifics of running a heart rate drift test can be found on the "How can I use this?" page.

In a well-trained aerobic system, when holding your heart rate stable at a moderate intensity during a one-hour workout, you should see minimal reduction in pace. However, when you exceed your aerobic threshold (the top of Zone 2 in a 5-zone heart rate model), your pace will begin to slow even while holding the same heart rate. This reduction in pace reletive to heart rate is what we are measuring and reading out on.

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What is my aerobic threshold and why does it matter?

Generally speaking, your aerobic threshold is the highest intensity (here, quantified by heart rate) at which your body is primarily using fat for fuel, with minimal stress on your cardiovascular system. This is helpful to know for a variety of reasons:

• Correct Training Intensity: Modern endurance training stipulates that the majority of your training (typically cited at ~80% of your total training volume) should be "easy". Your heart rate at your aerobic threshold is one of the simplest and most accurate ways to quantify this.
• Proper Race Pacing: By knowing your aerobic threshold, you can ensure that you are not exceeding your bodies capabiliteies during long races (typically cited at 3 hours or longer). When working above your aerobic threshold, your body uses gluclose stored in muscles as its main fuel source, which is much less plentiful than fat. Therefore, running above your aerobic threshold for a prolonged period of time will result in a rapid depletion of glycogen stores, leading to fatigue and a slower final time.
• Avoiding Overtraining: By keeping the majority of your training below your aerobic threshold, you can avoid injuries and burnout.