Why Running Performance Drops in the Heat
This weekend I had two athletes race the Brooklyn Half on the first truly hot day of the season… and it impacted their races. They trained in New York City all winter and spring in cooler temperatures, and on race day, they struggled more than usual.
When I looked at their running splits and data – it wasn’t an effort thing – their heart rates were high and that showed me they were working hard – but the heat really can’t be ignored. On our pre-race calls, we talked about adjusting paces and expectations as well as strategies for racing in the heat (pour water on your hands!), but it’s never easy to accept that you’ll have to run slower and there’s nothing you can truly do.
I also had one of my 1:1 athletes message me from Toronto because it unexpectedly hit 85 degrees there and her run suddenly felt terrible despite recently getting a 8 minute half marathon PR.
Here’s what you need to know about running in the heat, especially when it FIRST starts to get hot.
The good news is that our bodies DO adapt to the heat. But the bad news is, if you’ve trained in cooler temps all spring, you will feel what seems like a performance decline when the temperatures rise, especially at first.
How Age and Hormones Affect Running in Hot Weather
Two more things that you might not realize also impact your performance in heat – your age, and your fueling.
Perimenopause and Heat Regulation
Heat already increases cardiovascular strain, fluid loss, and recovery demands. But if you’re in your 40s & 50s and layer on hormonal changes from perimenopause, which can affect things like body temperature regulation, sleep, and hydration, suddenly the same run can feel dramatically harder.
Common Signs Heat Is Affecting Your Running
For a lot of women, this shows up as:
- overheating faster than they used to
- paces that normally feel easy feeling harder
- unusually high heart rate on warm runs
- feeling more wiped out the afternoon after your long run
- waking up hot overnight after evening workouts
- feeling puffy or inflamed even while training consistently
Why Under Fueling Makes Heat Running Worse
And often, the runners struggling the most in the heat are usually also trying to “eat lighter,” cut carbs, or unintentionally under fuel.
Why Carbs Matter for Hot Weather Running
But carbs help support glycogen stores, hydration inside the muscle, and overall stress response during training. When glycogen is chronically low, the body tends to perceive training as more stressful, and heat magnifies that quickly.
Tips for Running in the Heat During Perimenopause
If you’re feeling sluggish in training right now – slow down and run by rate of perceived effort, not heart rate, add more fluids & electrolytes, and make sure you’re eating your carbs! And, if you want to run in just a sports bra – GO FOR IT!
Why Summer Heat Can Help Fall Racing Performance
Be patient – because all this hot running over the spring and summer will lead to faster fall running.
Happy running,
Nicole Dobransky
PS If you’re wondering if I got close to puking at the 5K on Saturday – stay tuned for Saturday’s email.
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