Sometimes when I get hot and slow down in the heat I think I'm "just slacking" and being lazy. On today's track workout I wore my heart rate meter for the first time in a long time and it convinced me that it's not mental, it's really physiological! Not that I don't slack at times, but today my perceptions of exertion level corresponded exactly with my heart rates.
I had intended to do five miles on the track (including 1 mile of walking), but I didn't get there.
The numbers tell the tale:
Environment: 87*F, 75%RH, 0 mph wind, full hazy sun, 100*F heat index (I didn't look at this until I got home, or I might not have even gone out there).
Begin: Quarter mile walk warmup.
First track mile (I'm trying to take it very easy, just warming up):
11:16 min/mile, 154 beats/min average
Quarter mile walk recovery.
Second track mile (I'm still just jogging, but starting to get HOT):
12:03 min/mile, 166 beats/min average
Ugh. Half mile walking, trying to cool down, searching for a breeze.
Third track mile (It's absolutely frigging sweltering):
12:45 min/mile, 172 beats/min average
Once I get to the point I can barely maintain a jog and I'm still going into the red zone, it's time to call it a day. End of workout, four miles total.