I downloaded the data from my Garmin tonight for Saturday's race and it turns out that I had an average heart rate of 165 for the race, which is about Zone 4.8 for me.
That's two hours of nonstop anaerobic exercise with an average heart rate of 165. My maximum heart rate is 186.
Here's the lap-by-lap HR numbers:
Lap 1: Average of 169, max of 184.
Lap 2: Average of 162, max of 180.
Lap 3: Average of 165, max of 180.
My lowest HR for the entire two hour race was after a downhill on the second lap in which it dropped briefly to 124 bpm, before jumping right back up to 171 a minute later.
There were four instances during the race in which my HR dropped below 140bpm (all descents) and none of them lasted for more than a minute.
It's no wonder I was so tired after the race and this is really good information to have.
I train with a heart-rate monitor more than I train according to a heart rate monitor but I know when I race the 24hrs of Spokane, it's going to be imperative that I keep my heart rate below 140bpm the majority of the time, else there's no way I'll be able to go for long. I'm actually going to be trying to keep it pegged at 135 for as long as I can. I think focusing on the numbers on the Garmin (and the music on the iPod) will help take my mind off the pain of trying to ride a bike for 24 hours.