Some added context. After completing the half, I spent most of Dec doing easy runs using the MAF method (HR around 137 to 140) and saw incremental pace gains, although I was not at a calorie deficit. After reading about ADS, I was worried I was training too hard in my easy runs (I did not yet understand my Zone 2 HR could actually increase with training), so I thought I should dial it back significantly. After getting no drift in the HR Drift test at 125, I probably dropped too low. I’m thinking of targeting 135 on my next test, but maybe it should be 140?