How to Conduct the Heart Rate Drift Test
The heart rate drift test is used to determine your aerobic threshold (AeT). It is more accurate than the nose-breathing test suggested elsewhere on the Uphill Athlete website, especially if you are aerobically deficient(https://www.uphillathlete.com/aerobic-deficiency-syndrome/). The goal is to do the workout at what you think is aerobic intensity (below your AeT). You must exercise for an extended period—about one hour—and at a steady effort while recording heart rate and GPS data. Here is a video explaining how to do the test: https://www.uphillathlete.com/heart-rate-drift-test/

Watch this video after you have completed the test to set up your HR zones: https://www.uphillathlete.com/how-to-set-up-your-training-intensity-zones/

Where to do the test:

Outside: On a flat to very gently rolling course (running)

Inside: On a treadmill or stair machine

Do not do this test on an uphill/downhill out-and-back course. During the first half you will be going uphill and therefore doing more work, meaning the pace-to-heart-rate ratio of the two halves will be very different.

What you will need:
A GPS-enabled watch or phone
A chest strap heart rate monitor that pairs with your watch or phone (we recommend against using your watch’s built-in wrist heart rate monitor)
A TrainingPeaks Premium account (which you will have as a 2 week free trial as soon as you bought this plan).

The various metrics TrainingPeaks(https://www.trainingpeaks.com) provides are invaluable to athletes and coaches, and we gladly pay our fee to them (we receive no price break or kickbacks). However, you do need to have a TrainingPeaks Premium account to access the decoupling (heart rate drift) feature outlined here.

Should I run or should I hike? If you are going to be doing a lot of running in your training, do this test as a run. If you are primarily going to be hiking for your training, do this test as a hike on a treadmill or stair machine.

What should the effort feel like? This effort should feel easy and relaxed—a conversational pace. In other words, you should be able to carry on a conversation in full sentences.

Testing Outdoors
1.) Run, preferably on a flat (or very gently rolling) course at what feels like an easy aerobic pace. (See above for more detail on the desired effort.) If you have a good idea of what your AeT is, then target that heart rate for the beginning of the test.
2.) Once your heart rate stabilizes for 2–3 minutes after at least a 15-minute warm-up, start the recording feature on your GPS watch.
3.) Record for 60 minutes while doing your best to keep your heart rate close to that initial heart rate number.
4.) Upload the data to TrainingPeaks.
5.) Open the workout in TrainingPeaks and click the “Analyze” button. In the window to the right of your workout graph you will see Pa:Hr X.XX%. This decoupling metric compares the pace-to-heart-rate ratio of the first half of the workout to that of the second half. Note the number and skip ahead to “Reading the Results.”


Testing Indoors
1.) Set the treadmill to 10 percent and begin hiking slowly. If you are training for flatter runs, set the treadmill to 3 percent and run. (NOTE: If hiking, you may need to use a steeper grade—10+ percent—in order to get your heart rate up sufficiently.)
2.) Gradually build speed over the first 15 minutes until your heart rate stabilizes at what you feel is an easy aerobic effort for 2–3 minutes. (See above for more detail on the desired effort.) If you have a good idea of what your AeT is, then target that heart rate for the beginning of the test. Once you’ve dialed in the speed and grade, do not adjust them again during the test.
3.) Now you are ready to begin the test: Run or hike continuously for 60 minutes at that speed/grade while recording your heart rate.
4.) Upload the data to TrainingPeaks. Since GPS does not work indoors, the pace part of Pa:Hr will not be accurate. That is why it is so important that you hold the pace and grade constant once you start this test on a treadmill.
5.) Open the workout in TrainingPeaks and click the “Analyze” button. You will see a graph of your heart rate, pace, and elevation. To calculate heart rate drift, select the first half of the test in the graph and note your average heart rate in the window to the right of the graph. Then do the same for the second half. Compare the two numbers to determine the percentage rise of your average heart rate.



Reading and Implementing Your Results


3.5–5 percent: You have determined your AeT heart rate, which was your starting heart rate for the test. Set that as the top of Zone 2 in your TrainingPeaks zones. Subtract 10 percent from this and set that as the top of your Zone 1.


0–3.5 percent: The workout was within your aerobic intensity zones, but you should do the test again at a starting heart rate that is 5 beats per minute (bpm) higher.


>5 percent: Your initial heart rate/pace was above AeT. Redo the test using a lower starting heart rate. It may take several attempts to nail a decoupling that is slightly less than or equal to 5 percent.


Going Forward
Keep in mind that your AeT is not fixed. It changes day to day based on your recovery state and overall fitness. The decoupling (heart rate drift) metric is a convenient means of ensuring your workouts are within your aerobic capacity, and it can be used as an occasional spot check on your AeT.