I had set a challenge for myself, and I failed.
After I ran the Princeton Half Marathon in November 2021, I wanted to keep up my level of fitness without working too hard at it. I planned to run the half marathon again in November 2022, but didn’t want to train all over again from scratch. So I decided I would keep up my fitness by cycling up and down through weekly runs of 7 to 11 miles.
I charted my times for each longer run. Each time I repeated the same distance I wanted to run it faster than the cycle before.
That was working well for me for a while. But in July I hit a roadblock. When I ran 7.5 miles in July, I was quite a bit slower than my time for the same distance back in March. I was going backward.
My excuse? It was hot and humid out.
When it’s hot, you have to send extra blood to your skin in order to cool your body. Extra blood to your skin means less blood to your muscles. So you can’t run as fast.
I knew in a general way that heat would slow me down. But how much slowing would be the norm? And what’s the optimal temperature for running, anyway? I figured that there must be an answer to these questions, but I never was able to track the answers down, until a member of my Happy Trails Running Club linked me to an article in Outside magazine that addressed these exact questions.
They studied the results of a variety of marathons, tracking the temperatures and finishing times from year to year. You can read the article in detail. But I’ll summarize what I learned here:
- Heat and humidity will inevitably slow you down. Heat is the more significant and better-studied factor.
- The ideal temperature for running is between 44 and 59 degrees.
- For the average runner, for every degree above 59, you’ll typically slow down by about 2 seconds per mile.
- Running in the heat (with proper precautions and adequate hydration, of course!) does improve your fitness both when it’s hot but also under cooler conditions too.
Now I have a way to track my progress that accounts for changes in the heat. And another way to keep encouraging myself to set new targets for myself.