Run Like a Pro in the Heat and Humidity
By Dr. Trish Kana, PT, DPT
It’s July. You’ve set your alarm for 5am to get your run in before the heat of the day becomes unbearable. You wake up to 100% humidity and 79 degrees and you’re wondering if you’ll be able to breath on your run because it feels like a swamp outside.
Sweating while we exercise helps cool us down, but high humidity makes it harder for the sweat to evaporate which is the crucial part of the cooling process.
It’s tempting to ditch the outdoor run plan and hop on a treadmill (and sometimes, this is the safer choice). But there are benefits to training outdoors in the heat/humidity. You can gradually adjust to training at higher temps. In fact, research suggests that just 2 weeks (14 days) of heat training can lead to acclimatization, allowing you to feel and perform better in conditions that at first made you feel like a hot mess.
So how should we adjust our running during this time?
First- slow down the pace. The chart below shows recommendations of percentage pace adjustment based on the combined dew point and temperature. Dew point is not the same as humidity % but is an important and easily accessible metric to find on most weather apps/sites.
This chart is useful to calculate how much you should slow down based on the combination of temperature + dew point.
As you approach the 185+ region, this is when you should think about skipping the run or taking it inside as the combined temperature and dew point makes for risky running conditions.
Second (and this may be obvious), but HYDRATE! Especially if you are a morning runner, give yourself time to sip at least 6-8 ounces between when you wake up and when you start running as we become dehydrated while we sleep. Plan your route around known water fountains or carry a pack/water bottle- aim to get in 400-800ml of H2O per hour of running. You lose salt with your sweat, so make sure you’re supplementing during and/or after your run with enough electrolytes. Depending on the runner, moderate intensity running can result in anywhere from 300-1500mg of sodium per liter of sweat lost.
Third- limit your caffeine intake before a run. Caffeine is bladder irritant meaning you have to pee more frequently. And in the heat you really want to retain as much fluid as you can to stay hydrated.
Fourth- pick light-weight, light colored, and moisture wicking clothing. Avoid the heavy cotton and dark colors as they can trap heat and moisture and make it even harder for your body to cool itself down. Some athletic gear is even made with UPF material to protect against harmful UV rays.
After just 2 weeks, you could notice a difference in your perceived level of exertion and effort when running outdoors in the grueling temps. AND, as the dew point starts to drop and the temps along with it as we enter early fall, you’ll feel lighter and easy breezy on runs. Maybe your easy pace will get faster or you notice your heart rate is actually lower on your easy runs.
Remember to listen to your body. If you’re feeling sick, nauseous, dizzy, or lightheaded- stop running! Make sure you hydrate, get those electrolytes, and get yourself to cooler temps to allow your body to recover.