One of the things that depressed me about the past weekend's rides was my inability to get my heart-rate into zone 4 for any length of time. My "perceived exertion" was 8 or 9, so maybe my mind was playing tricks on me. I thought I'd trained better than that.
However, after a day of rest I reviewed my stats again and saw that the average heart-rate of 133 fell above the zone 4 minimum. How strange! Obviously, with more oxygen to the brain, I concluded my computer zones were out-of-whack. Of course! I hadn't reset everything when it came back from Garmin. A few quick clicks showed me the computer thought my max HR should be 185 when in reality it is 167 (or was last year when I challenged Courtyard). Much better.
I had cleared the memory when moving the data to my spreadsheet, so I can't re-calculate the time spent in zone 4, but I can look at the chart and get a good idea. Yes, I deserved to feel as wiped out as I did. Most of the time was low zone 4.