- At the end of the first block, my HR was 164 bpm. It dropped nearly 60 bpm to 106 bpm during the recovery. An encouraging sign.
- 2nd block, I started to run into trouble. My HR hit 170 bpm by the end of the 10 minutes. This is in the anaerobic zone for me. The HR dropped 55 bpm to 115 bpm during the 2nd recovery zone.
- 3rd block, I knew I was done. After 8 mins @ 7.5 mph, I was already back up at 170 bpm. So I shut it down.
EpilogueAs I promised, I tried again today after work. Monday's results are obviously significantly better than Saturday's. Instead of three 10 minute blocks at 7.5 mph, I got nearly four 10 minute blocks in at 7.5 mph. (And getting in the target 5th can't be far away.) As a result I burned 615 kcal on the treadmill instead of 467 kcal on Saturday. Plus another 321 kcal on the spin bike afterwards gave me a satisfactory Monday total of 936 kcal. I call that a good start to the week. Obviously, there are no scientifically valid improvements in aerobic capacity that are realizable in only 3 days. The red line is the heart rate.
- As the graph shows, I reached 165 bpm at the end of the first block. It dropped to 110 bpm (55 bpm delta) on recovery.
- 2nd block, I reached 170 bpm, dropping to 119 bpm (51 bpm recovery delta).
- 3rd block, I reached 172 bpm, dropping to 125 bpm (47 bpm recovery delta).
- 4th block, I hit 172 bpm by minute 7, so I shut it down at minute 8. If I had persevered, the recovery would have been worse again.
(Incidentally, same thing is true for weight room workouts. Initial gains cannot be from muscle size adaptation.) The other effect is learning to survive at the higher heart rate (HR). Back when I used to train on the bicycle, I called it "learning to live in the 170s", i.e. getting used to the HR staying in the 170s bpm range for an extended amount of time. Of course, as aerobic improvement accrues, the sustained HR will drop for any fixed speed.