Running in the Heat: 4 Top Tips

I don’t know what the weather is like where you all live, but here in Massachusetts the last few days have passed 90 degrees.  Don’t get me wrong – I’ll take the heat over the massive snowstorms we had all last winter.  But hot and humid weather can make it a bit tough to train outside.  I’ve put together 4 top tips for running in the heat below.  I know I get a bit sciencey at parts in this post, so forgive me if it sounds a tad impersonal – but I’m hoping this info is useful for you!

4 Tips for Running in the Heat

1.  Hydrate properly

Drinking enough fluid is essential to staying healthy while exercising on warm days.  If you’re working out for more than 60-75 minutes, it’s smart to take in fluid + electrolytes + carbohydrate.  If you’re working out for less than 60 minutes, plain water is generally fine.  If it’s a really warm day though and you’re out there less than 60 minutes, drinking an electrolyte beverage without carbs – like nuun tablets or something similar – might be helpful.

I’ve found some runners get nervous about drinking on runs, because many have seen media stories about overhydrating and getting sick from too much water intake (otherwise known as hyponatremia).  That is a very real concern with serious consequences – however, dehydration is about six times more common in runners compared to hyponatremia.

The key is to drink enough to maintain the right balance; to prevent dehydration without risking hyponatremia.  There’s no one guideline that fits all people for proper hydration.  I can’t say drink x ounces per hour because we all sweat at different rates – person A may lose much more per hour than person B – so hydration recommendations really should be personalized.

My advice is to do a “sweat test” to see if you’re hydrating right on hot days – weigh yourself before and after a run in the heat.  If you lost more than 2-3% of your body weight, you probably want to hydrate a bit more.  If you stayed exactly the same or you gained weight, you should hydrate a bit less.  If you lost about 1-2% of your body weight, you’re probably in the sweet spot of proper hydration.

Even with a sweat test, above all – pay attention to your body’s cues for thirst (dry mouth, craving water) and overdrinking (sloshing, nausea) – and be sure to honor those cues.

And of course, if you’re training and you start to experience any warning signs of heat related illness or hyponatremia, stop and get help.  Heat exhaustion may present itself with lightheaded, dizziness, confusion, muscle cramps, nausea/vomiting.  Hyponatremia often presents with similar symptoms, and can dangerously progress to issues like seizure or unconsciousness.

2.  Acclimate for hot weather events

The first question I usually ask people when they’re planning to train throughout the summer for an event:  Is your race going to likely be in warm weather too?  If race day is almost always a cooler day, then there’s really no reason to subject yourself to training in hot weather.  Do your training in the early morning or later in the evening when the temperature cools down.

If it is going to be warm on race day, though, it’s important to do some of your training in the heat so that your body can acclimate to the warm weather.  It takes your body a bit of time to get used to running in the heat – about 2-4 weeks depending on your fitness level, training schedule, and the specific weather conditions.  When you start exercising in the heat, start with a slower pace and reduced intensity at first.  After a few weeks, your body increases plasma volume to help carry blood to the surface of your skin to dissipate heat, and you also become a more efficient sweater (starting to sweat earlier for cooling, and losing less sodium in that sweat).

All this being said, train smart even if your race will be in hot weather.  If there is a major heat advisory out there, it’s not the time to try to prove your superhuman strengths with a mid-day long run.

3.  Focus on sodium

Sodium is important for runs (or other exercise) lasting over an hour.  In the heat, it becomes even more important since you’re sweating more frequently and losing electrolytes.  Sodium recommendations are also hard to give as generalized advice, because the rate at which people sweat varies considerably, as does the concentration of sodium in a given amount of sweat.  As a starting point, the ACSM recommends that you take in about 500 to 700 mg of sodium per liter of fluid you drink during exercise that lasts more than an hour.  Most commercial sports drinks fall in this range.

If you’re a heavy salt sweater or you find yourself struggling in the heat, you may need a bit more.   I generally recommend trying one of two options for this:

• Try a sports drink with a higher amount of sodium (for example Perform or Gatorade Endurance Formula)
• Add a pinch of salt (1/8 tsp) to your normal sports drink

You could also consider electrolyte tabs or capsules.

{Side note – I highly recommend sitting down with a sports dietitian (myself or others) who can help you figure out the right hydration, electrolytes, fuel etc for your particular body.}

4.  Try a pre-exercise ice slurry

An ice slurry or slushy is basically just crushed or shaved ice mixed with water.  Interestingly enough, this has been researched several times in sports nutrition journals.  The findings are generally consistent that taking in an ice slurry before going out to exercise may keep your core body temperature cooler during your run.  There’s less research on the role during a run, but on a really hot day I think (anecdotally) it could be worth a try if you’re running by your house multiple times (or the ice cream man swings by with some snow cones, haha).

Share with me:  What are your tips for running in the heat?  What tip above will you start to implement?

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Chrissy Carroll

Chrissy Carroll is a Registered Dietitian and USAT Level I Triathlon Coach. She specializes in sharing nutrition and fitness tips, as well as recipes, for runners, triathletes, and active women.Chrissy holds a Bachelor's Degree in Nutrition, a Masters Degree in Public Health, and is also an ACSM Certified Personal Trainer.

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