I had a hard time on my "easy" run this past Tuesday. I used my heart rate monitor and tried to train within 60-70% of my heart rate reserve, as per the Karvonen method. Still, I registered an average heart rate of 144 (72%), and felt very sluggish on the run (4.31 miles). I ran in 44:08, a 10:14 pace, and it felt like it.
So today, I wanted to try something. I ditched the heart rate monitor and ran by how I felt. I wasn't going to concentrate on numbers, just with "running easy".
And something weird happened.
I ran the same course, same time of morning, did the same pre-run warmup and stretch, and drank the same amount of water and juice as I did on Tuesday. The only difference was that Tuesday was about 8 degrees colder than today. But this morning, with no heart-rate monitor, I ran that course in 42:48, or a 9:56 pace. I felt so good at the end of the run that I could have kept going. On Tuesday, I couldn't wait to finish.
Huh? What gives?
I'm at a loss to understand how, running much easier today than I did on Tuesday, I was able to run at a pace 18 seconds faster than the easy run I struggled through on Tuesday. And I felt much stronger today, with a restless night of sleep, even.
I'm not complaining - I'm just baffled. I have been a big proponent of heart rate training since I got the device last year, but this throws it all out of whack now. Do I now run by feel rather than trying to stay within a heart rate range? Or is it that maybe my resting rate has declined to the point where my range is lower than what Karvonen dictates? Possibly my heart rate monitor is faulty - it has been acting strangely the past few weeks.
Nevertheless, I'm going to give it (no monitor) a try again tomorrow morning. I'm running back-to-back days to get some mileage in before the predicted snowstorm hits tomorrow afternoon. If I do another 4.31 miles tomorrow, I can do an easy 4 to 5 miles on the treadmill on Sunday without my mileage dropping too significantly.
Just over 6 weeks to the National Half Marathon!