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Cooler weather means faster training runs: 8:30 pace in 80 degree weather means 7:30 pace when temps are in the 60s

Posted Sep 20 2011 11:09am

The end of summer is not until Friday, but already the cool temperatures – and cool is a relative word since the morning lows are in the low 70s instead of the low 80s – are positively effecting my runs.

On Monday, I had my first marathon-goal pace run. I ran 9 miles with the first three as a warm-up. I wore my heart rate monitor, which gave me some interesting feedback, confirming two critical points:

1) When my heart rate is 80 percent of max in cooler weather – say anything  under 75 degrees – my pace is  30 seconds to a minute per mile faster than when it is as oppressively hot as it has been this summer.

2) There is marathon goal pace (MGP) and anything faster than that is a pace that I wouldn’t wanna play around with on more than a one or two mile basis – or a race. During my pace run, it seemed like I could comfortably run 7:20 to 7:30 pace and anything faster than that meant I had to try too hard.

That’s how it felt effort-wise and as I look at the feedback provided by my heart rate monitor, 7:25 min/mile acts as a line of demarcation. Anything slower felt easy enough, like a half-marathon pace at this speed would be a cakewalk. And anything faster was a little harder than I wanted it to be.

Here are my mile splits and heart rate for Monday’s run:

The middle miles of Monday's MGP run


Back to the weather: Today (Tuesday, Sept. 20), I ran a little more than 7.5 miles. It was the usual Luke’s Locker taco run. The temperature was 65 degrees with little humidity. My average pace for the entire run was 7:28. A month ago, on Aug. 23, I ran this same route at the exact same time of day and my pace for the run was 7:59. The temperature was near 80.

Here is a screen cutout of both runs inputed in my Garmin Connect, with today’s faster run on the left and last month’s hotter run on the right:

Legs had a last-mile party at Mile 7. I need to save that for the marathon, though.


So, right there, a 15-degree temperature change gives me about a 30-second pace differential. But its more than that. On Aug. 23, I stopped for water twice and felt like I couldn’t go another mile. But today? No water until the end of Mile 7. And as you can see, my legs were really wanting to party with the 7:01 on Mile 3 and the 6:33 on Mile 7.

After the water break, I still wanted to run – however, it was time to get home to get dressed for work – so I threw in a little cooldown, and even that was pretty quick for a cooldown.

The key for the next few months, until the Dallas White Rock Marathon, is not to get too carried away. I’m gonna work around the 7:25 to 7:30 pace on non-recovery runs and try not to go any faster – no matter how good I feel.

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