I just got back from my second attempt trying to pinpoint my aerobic threshold via the heart rate drift test. My first attempt 2 weeks ago resulted in a 1.5% heart rate drift, so I tried again at a faster heart rate today.
I ran to a quarter mile flat loop that’s about a half mile from my place, did the hour long workout and ran back. While I wasn’t always right at my target heart rate, I stayed within a few bpm on either side the whole time. The result I got was -0.5%, somehow at a faster pace my results are showing a lower heart rate drift.
My first thought was faulty data, but everything looks fine to my eye. My GPS didn’t act up and ping me somewhere I wasn’t and my heart rate as recorded by my chest strap monitor looks like it has a normal fluctuation, although I am new at using heart rate data. My next thought is that I conducted the test wrong. I tried to control everything I could; I ran in the morning so the temperature change wouldn’t be significant, I ran a small flat loop, I ran to the workout and started straight away so my heart rate would already be stable. In re-reading the instructions I picked up on this line:
“when you are operating in Zones 1 and 2 (intensities at which your aerobic metabolism is providing the bulk of the energy needed), your heart rate increases in lockstep with your pace if your movement economy is uniform throughout these lower speeds”
At the beginning of the workout I had a hard time getting my headphones to stay in, so I was reaching up to fix them a lot. Could that have affected my movement economy enough to nullify the results? Does anyone have any other ideas? I’m going to try the test again at a higher hr, but if I’m doing something wrong I’d like to figure that out first.