Heart rate drops in third effort of The Cobbler

I did The Cobbler today for the first time (now that’s enterPAINment!) and I was watching my HR to try to follow the guidelines in the very detailed workout instructions. In the first two long efforts it was within the 95-98% of cTHR that were indicated, but then in the third effort it dropped to below 90% of cTHR, even though I hadn’t adjusted the power targets and was still able to meet them, and my RPE seemed right, gradually increasing. It did bump up a bit towards the end of the third effort, but since the instructions specifically say that your HR should stay in the 95-98% range, I was left wondering. I know that HR will tend to drop at the same RPE later in a workout, but how is it possible to have a lower HR but still meet the power targets later in the workout? I would have thought those had to go in lock step as the heart is delivering the oxygen needed to produce power. Or is this an indication that my HRM is not functioning properly? I actually stopped and replaced the battery in the HRM to make sure that wasn’t the issue.

I don’t remember the third effort in Cobbler, but isn’t that the one that is done at a much lower cadence? If it is, and you are well trained, your heart rate will drop. It is not cause for concern as this is really normal. My HR stays in Zone Three-Four for 85-90 RPM efforts but will drop into Zone Two for the same efforts at 50-60 RPM.


interesting you post this, i just did cobbler today and after reding your post checked mine. my HR also down a little in the third interval. suggest it’s nothing to worry about and if anything a good thing putting out same power at lower HR effort


All three are at quite a low cadence, but you are correct, the third one is lower than the other two. Maybe that explains it.