Trail Running Tips for Staying Hydrated in the Heat

It’s summer, and the trails are beckoning. But in a rush to play outside it’s easy to overlook preparation for running in high heat.

running in summer
Photo: Unsplash

When the body’s temperature rises above 103 degrees, power and performance drop, and outdoor adventure can quickly turn into scary heat-related exhaustion or stroke if you’re not thinking ahead.

To learn what runners can do to stay hydrated and healthy before, during and after a summer run, we talked to Dina Griffin, a board-certified sport dietitian who works with endurance athletes of all ages in Boulder, Colorado. These tips are especially important on the trail, where runners can get dangerously far from necessary aid.

First, sodium: If you lose too much via sweating that’s not good. Sodium is responsible for controlling the total amount of water in the body. It also regulates blood volume and helps maintain muscle and nerve function.

But it’s important to note that your body’s sodium concentration can vary greatly from your buddy’s. Griffin tests her athletes and has found a large variance in the “saltiness” of athletes’ sweat.

“Then when we factor in one’s sweat rate [or how heavily a person perspires], this can dramatically affect hydration strategies,” she says. “It’s not usually possible to replace all fluid losses from sweat, especially for heavy sweaters, but a general fluid intake range is 16 to 32 ounces per hour.”

If you really want to fine-tune your hydration, learning your personal sweat rate in a variety of conditions is a great place to start.


running in heat
Photo: Pexels

Time it up. “When doing early-morning trail runs you are not going to be well-hydrated to start. It’s nearly impossible,” Griffin says. “So plan to drink fluids during the run or put a focus on rehydration when returning from the run.”

You do you. “There really is no foolproof formula for how much to drink prior to starting a run,” Griffin says. “It really depends on the athlete.” Age and athletic ability come into play, but so does the specific workout – how long and hard you plan to run – and the weather conditions, temperature and vertical gain. Finding your personal hydration harmony takes some trial and error.

Enjoy a cup of Joe. Coffee and tea are not going to dehydrate you, so it’s OK to stick to that morning ritual prior to a trail run, according to Griffin. “Though I would still recommend getting in some plain water!” she cautions. Think about getting in at least two glasses of lemon water before that first cup of Joe.


running in heat
Photo: Unsplash

Dial in electrolytes. If the run is short, water is fine. “If you’re going longer in the heat, sodium is the most important electrolyte to replace during or after a run,” Griffin says. “Many sports drinks are too concentrated in carbohydrates and sugar (which is defined as “high osmolality”). High osmolality of blood means you’re dehydrated and low osmolality means you’re over-hydrated. Neither is good. Your body needs a balance.

So load your handheld with an electrolyte replacement, like Skratch or Osmo (which makes a women’s-specific formula), that’s in the 3 to 4 percent range.

Keep an eye on GI. Runners who follow poor hydration strategies can go into gastrointestinal distress. “This could be because of too many calories consumed, the ‘wrong’ mix of calories, or not enough water to help with proper hydration and absorption/digestion of calories,” explains Griffin.

Yeah, EAH is real. Exercise associated hyponatremia is a dangerous condition that occurs during or immediately following a run when the body’s blood-sodium concentration gets dangerously diluted. Signs can include impaired exercise performance, nausea, vomiting, headache, bloating and swelling of hands, legs and feet.

“It’s not super common, but may be happening more than we realize,” Griffin says. EAH can come on during a long, hot run when you’re sweating heavily and not drinking enough sodium replacement. So be mindful to replenish the body often, especially if you are feeling any of these symptoms.


Photo courtesy of Skratch

Stick to sodium. Again sodium is the key electrolyte we lose in sweat. Don’t get sucked into “healthy” alternatives that don’t give the right return. For example, “runners who guzzle coconut water are getting far more potassium than sodium, so it’s not a beverage I recommend exclusively for rehydration,” says Griffin.

Don’t overdo protein. Athletes were once taught that protein was a paramount part of recovering – but that doesn’t hold true anymore, says Griffin. It depends on an athlete’s pre-run protein consumption, total daily protein intake and training volume or training block, but “most runners don’t need to pound a huge protein shake in that critical 30-minute post-run window,” she says. “A common mistake is overdoing calories and protein in that immediate window when it simply may not be necessary.”

Sure, drink a beer. Let’s face it, beer is a popular post-run drink. “It’s not as evil as we once thought, yet the issue is that we may neglect other hydration [like water] and choose suboptimal food [like fried foods or sweets] once we start drinking,” Griffin warns. Just keep in mind that the general rule of drinking 16 to 24 ounces of fluid for every pound of sweat loss still stands.

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