Fuel from the Road: Tips On How To Stay Cool While Training In The Heat

Fuel from the Road: Tips On How To Stay Cool While Training In The Heat

Pamela M. Nisevich Bede MS, RD, CSSD, LD 

This morning’s run in hot and humid conditions reminded me of how performance can really falter when the thermometer reads red.  Indeed, only a few miles from the office, I was certain I’d have to call for a ride home.  Having gone out for a 10mile tempo session without the aid of hydration and electrolytes was a rookie mistake but even the most seasoned runners can empathize with how difficult it can be to stay hydrated during summer runs. 

When exercising in extreme conditions, certain physiologic actions occur to keep your system cool; skin blood flow and sweat rate increase to allow for heat dissipation to your surroundings. These actions have a clear and useful purpose but demand you to drink up or else as you sweat and cool off, the potential for dehydration arises. This dehydration can lead to increased body temperature and heart rate and eventually your performance can suffer. Fortunately, research suggests that these are some simple actions you can take to sustain your performance during training and racing in the heat, as well as minimize the risk of heat illness. 

Heat acclimatize

Why? Heat acclimatization- or training in the heat- is essential in order to cope, workout, and even race in hot and humid environments. The more trained you are, the quicker you can adapt to heat and for most all athletes, acclimatization takes 6-10 days of hour-long sessions but it take up to two weeks to fully acclimatize and optimize performance in the hot conditions. In order to acclimate, you’ll need to increase body temp in order to induce profuse sweating and increase skin blood flow. As a member of MIT, if you’ve been running outdoors in Ohio, you should be acclimated by now.  But just in case you’ve been doing all your training on the treadmill in a room with AC, as you transition to outdoor runs, you’ll naturally acclimate- just be patient. You end goal should be to find an environment similar to race day in which to train. Maybe this means finding a humid indoor gym, maybe it means exercising at a time of day when you’d normally stay indoors. Of course, for safety’s sake, read the hydration tips below, listen to your body, and avoid the obviously unwise practices and gear such as sauna suits and beginning a run low on fluids.

Time to Hydrate

The question whether dehydration significantly impairs performance might be up for debate in some circles but years upon years of data has found that dehydration can derail performance. Numerous studies have found that dehydration in excess of 2% loss in body mass impairs performance, yet other studies have found that elite athletes tend to finish races dehydrated well beyond 2% (the lighter load potentially contributes to a faster time) and a few studies have shown that dehydration of close to 4% (in cycling) didn’t impair performance in well-trained athletes. To hold the middle ground, many experts suggest simply drinking to thirst in order to avoid dehydration and overdoing the fluids and ending up hyponatremic. That being said, if you drink to thirst over a long and hot run, you’re likely to finish in a dehydrated state and your perception of thirst and drive to drink may be altered during exercise. In general, here’s how to start (and even finish) a run properly hydrated;

  • In the days and hours leading up to a race or workout, drink sufficiently and replace electrolyte losses. You can find these electrolytes or minerals in food or in sports drinks. Ones to look for: sodium, chloride, and potassium. Calcium and magnesium are also lost but to a lesser extent. Additionally trace minerals including zinc, iron, iodine, and others may be lost but in very small amounts.
  • Aim for a fluid intake of approximately 1oz per 10lb body weight every 2-3h throughout the day as well as 2-3h before a training session or race.
  • Know your sweat rate by weighing in before and after a run. Once you know how much sweat you lose during an hour of running, you can plan ahead to know how much you need to drink during the run and also how much electrolytes you likely need (see last tip).
  • Keep it cool at the start: Cold water immersion (like a cool towel draped around your neck) and cold slurry ingestion (chewing on cold ice chips or downing an iced slurry) before a workout likely help cool the inner core and keep you cooler, longer.
  • The sweat you lose needs to be replaced following a run. Aim to replace at least 100% of what you lost (i.e. drink 16oz for every pound you lost) and if you have another workout within 24 hours, aim to replace ~150%. 
  •  The main electrolyte lost in sweat is sodium and different athletes lose different amounts. Traditional sports drinks don’t provide nearly enough electrolytes for the majority of athletes and salty sweaters, who can lose 460-1610mg of sodium per liter of sweat, respectively. Sample EAS BCAA + Electrolytes as you run along with MIT; it’s scientifically designed to replace key electrolyte losses and the BCAAs help you maintain mental focus and proactively recover as you run. 

In summary, while many of us would prefer a mild spring day over the heat of August, like it or not, summer will be with us for a while. Fortunately, by putting into practice some of the tips above, you can make the most of every workout, run, and game this summer.

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