With the usual strange Chicago weather the past week, I was able to really see the impact of high temps / dew points. I ran 9 miles (1 easy, 7 M pace, 1 easy) on both Sept 26th and Oct 3rd on the same trail with very different results:
.........................................26-Sep...............3-Oct
Temp + DP......................92 (50+42).......156 (88+68)
Plan Total Time (hrs:min).......1:57.................1:57
Plan Pace (min:sec)..............12:38...............12:38
Actual Time...........................1:51.................2:03
Actual Pace..........................12:18...............13:36
Average Heart Rate.................125..................149
Max Heart Rate.......................146..................180
I think the heart rate data tells the story. My max HR on the cool run was less than my average HR on the hot run. The faster cool run felt really good, almost too easy to be a
@DopeyBadger "hard run". The slower hot run was very difficult, and I felt completely drained afterwards. I slowed down and walked a bit more when I noticed my HR was in the 170's for a 60 year old guy. The 12 minute difference in time was not as significant as the effort, which was like day and night (or perhaps like cold and hot).
Nine days until my first marathon, which will be on the same trail. I can only hope the weather is more like last Wednesday than yesterday. The forecast is showers and 53 degrees, but that will change frequently.