Clarification on Treadmill Cardiac Drift Test | Uphill Athlete
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Topic
• #42845
giohunt
Participant

I’m confused a bit about the right way to interpret a treadmill AeT test.

Let’s say that I believe my AeT threshold is 140bpm. So, after a good 20 minute warmup, I begin the recommended treadmill test (constant grade and pace) with a starting HR of 140.

My HR at the beginning of the test is 140bpm.
After 30 minutes, it’s 147bpm.
After 60 minutes, it’s 154bpm.

So, over the course of the hour-long test, my HR increased, essentially linearly, from 140 to 154.

Therefore, my average for the first half of the test is 143.5.
And my average for the second half of the test is 150.5.
150.5 divided by 143.5 = 1.0488% So, using this averaging method, I’m inclined to conclude that this was a successful test. And my AeT is equal to my starting HR of 140.

HOWEVER, here’s the part that is confusing to me. At the beginning of the test my HR was 140. At the end of the test my HR was 154. So, from start to finish, that’s a drift of 10% (154/140), which seems like a fair amount of drift in an hour, right?

So, two questions:
1. Is this OK? Did I do the math correctly using the averaging method? Is it right for me to conclude that my AeT is 140 based on the test above?
2. The treadmill test seems like a weird way to test for AeT. Basically, the whole hour long test is done with a level of exertion ABOVE what we think is the AeT. For example, in the above test, I started by thinking my AeT is 140, but tested it by running ABOVE 140 for an hour (i.e., by running in Zone 3). Wouldn’t the amount of cardiac drift ABOVE AeT really be more a test of how efficient my ANAEROBIC engine is? I don’t quite understand how the amount of cardiac drift while working ANAEROBICALLY can be an indicator of where my AEROBIC threshold is. Is this just something you guys have observed enough to know works as a test for AeT?

Thanks is advance for any guidance you can provide. And thanks for fostering such an amazing community of knowledge sharing.

• Inactive
Anonymous on #42862

Therefore, my average for the first half of the test is 143.5.
And my average for the second half of the test is 150.5.

Don’t average the starting and ending values; let Training Peaks calculate the averages. The rise isn’t purely linear–there will be a lot of fluctuation–so the TP algorithm would give a more reliable average.

Then you want to find the drift in the averages, not the starting and ending values.

2. The treadmill test seems like a weird way to test for AeT. Basically, the whole hour-long test is done with a level of exertion ABOVE what we think is the AeT. For example, in the above test, I started by thinking my AeT is 140, but tested it by running ABOVE 140 for an hour (i.e., by running in Zone 3).

You’re assuming that your estimate is correct. The drift test confirms or denies that estimate.

Rather than focus on heart rate, think about it from the pace side. If you warm-up and then go at X pace for 60′, and if you see an HR drift of 5% or less, then you can assume that that pace is equal to or less than your aerobic threshold. If you are training on the treadmill, use the pace. If you are in variable terrain, use the heart rate.

Heart rate is a stress measurement. So as stress increases so will heart rate. Duration is one kind of stress. By observing many hundred athletes, a decent rule of thumb was developed: if a pace elicits a 5% or less drift in HR, then it’s likely within the aerobic threshold.

Participant
giohunt on #42876