yeah I noticed that on some thread, jealous! My last long interval was outside about 3 weeks ago, and included a 2-hour interval at 78% average power which is lower tempo. Had 0.05% cardiac drift on that one. I started TB1 the last week of August, my drift then was 15% but within two weeks it was under 5% and kept going down from there. That is pretty typical for me, and all I’ve noticed with cardiac drift is that it jumps up a little (but still under 5-6%) if I’m forced to take 3 or 4 days off because of travel. Given that, I don’t pay too much attention to cardiac drift as an indicator of diminishing returns.