Today is a rest day, but I measured my wakeup HR to see if it would stay below 50 (see yesterday's post) or return to its normal range of 50-52. It returned and was 50. I had a good 8 hours sleep and was hopeful that might "induce" my HR to be low again.
Back in the early 80s when I ran marathons, my wakeup HR was 44. It had been 44 for a year or two. One day it was 40, and I thought it was just a fluke. However, it stayed at 40 for the remainder of my marathon training. I'm expecting that my wakeup HR will drop into the 40s as my body gets used to longer distances. In the past two years I've had my wakeup heart rate go into the high 40s on several occasions and them return to the low 50s.