Running in the Heat Without Wrecking the Season

Full Transcript

Running in the Heat Without Wrecking the Season

Cold Open

Third week of July, a few summers back. My team is out for a tempo run. Eighty-eight degrees, dew point sitting at 74, the kind of morning where the air feels like a wet towel over your face.

I’ve got a freshman in the group. Good kid, tough kid. And about a mile in she’s already breathing like it’s a race, her form is falling apart, and she says the thing I’ve heard a hundred times. She says, “I’m fine, Coach. You just get used to the heat.”

She was not fine. She finished that run twenty seconds a mile slower than she’d go in October, her heart rate was fifteen to twenty beats higher than normal at the same effort, and here’s the part that actually worried me. In her head, she didn’t just have a hot run. She decided she was out of shape. She took a physics problem and turned it into a story about herself.

That’s the whole reason for this episode. Because right now, this very week, there’s a heat dome parked over most of the country, and thousands of coaches are about to let their kids make that exact mistake.

Intro

Welcome back to Salty Talks. I’m Coach Saltmarsh, twenty-five years on the track, thirty-one state champions, and today, one strong opinion I want you to walk away with. Heat is not an obstacle to grind through. It’s a variable to manage. The coaches who get that get more out of the summer. The ones who don’t spend all of September wondering why their team looks flat.

And look at the timing on this. As I’m recording, there’s a heat dome building over the Mississippi and Ohio Valleys and the whole Southeast. Heat index numbers between a hundred and a hundred and fifteen degrees, days in a row, no relief overnight. Raleigh, North Carolina and Tallahassee, Florida are literally under an “extreme risk” heat classification. If you coach in that footprint, this episode is not theory for you this week. It’s Monday’s practice plan.

So let’s do it. Why heat slows you down, the one number you should actually be watching, exactly how much to back off, and the safety line you do not cross. Let’s go.

Segment One · Why Heat Makes You Slow

Start with what’s actually happening in the body, because if you understand the mechanism you’ll make better calls in the field.

When your athlete runs hard, her muscles throw off an enormous amount of heat. During hard exercise the body makes something like fifteen to twenty times the heat it makes sitting still. And all of that heat has to go somewhere, or her core temperature climbs into a range that will hurt her.

The main way she dumps that heat is sweat. But here’s the piece most runners never get told, and I want you to say it to your team this week word for word.

Sweat does not cool you. The evaporation of sweat cools you.

Sweat that just rolls off her chin and hits the pavement did almost nothing. It cost her fluid and bought her no cooling.

So now picture a dry day. Sweat evaporates fast, pulls the heat right off the skin, she cools well. Now picture a soupy, humid day. The air is already full of water, the sweat has nowhere to evaporate to, it just runs off, and the cooling system stalls out.

When that happens, the body does something clever and expensive. It sends more blood to the skin to try to shed heat that way. But that blood is getting pulled away from her working legs. So now her heart is doing two jobs at once, feeding the muscles and cooling the body, and it does that by beating faster. That’s why her heart rate is fifteen, twenty beats higher at the exact same pace. Research on running in humid heat shows exactly that jump.

So when your athlete tells you her easy pace suddenly feels like a threshold effort, she is not being dramatic. In bad air, at the same speed, the cost to her body really did go up. She’s right. She just needs you to explain why.

Segment Two · The One Number That Matters

Here’s where I’m going to change how a lot of you check the weather.

Most coaches and most athletes look at two things. Temperature, and relative humidity. I’m going to tell you to mostly ignore both and watch a third number. Dew point.

Let me explain why humidity is a junk number for us. Relative humidity is a percentage. It’s telling you how full the air is compared to how much it could hold at that temperature. But the air’s capacity changes as it heats up and cools down all day. So you can see eighty percent humidity at seven in the morning and forty-five percent by noon in the exact same air, with the exact same amount of water in it. The number swung. The moisture didn’t. It’s lying to you.

Dew point doesn’t do that. Dew point is a straight measure of how much water is actually in the air, and it does not swing around with the temperature. A dew point of seventy means the air is loaded, full stop. Which means sweat can’t evaporate. Which means your kid can’t cool. That’s why every experienced coach I know tracks dew point and barely glances at humidity.

The quick mental map is this. Under fifty-five, you’re golden. Fifties, comfortable. Low sixties, you’ll start to notice it. Mid to upper sixties, it’s real, and both easy and hard days need adjusting. Seventy and above, that’s a hard day just to be outside, and you’re running by effort and treating it with real caution. I’ll give you the exact pace numbers in a minute.

And here’s the part that surprises people, the part that makes the whole case. A ninety-degree day with a forty-five-degree dew point is honestly easier to run in than a seventy-five-degree day with a seventy-two dew point. The hot dry day looks scarier on the thermometer. The warm sticky day is the one that puts kids in the medical tent. It doesn’t feel as dangerous as it is. That’s exactly what makes it dangerous.

Segment Three · How Much to Back Off

Okay. You’ve got the dew point. How much slower should they actually run? I’m going to give you real numbers, not “take it easy out there.” Work off the dew point.

Under fifty-five, no change. Fifty-five to fifty-nine, about one percent slower. Sixty to sixty-four, three percent. Sixty-five to sixty-nine, five percent. Seventy to seventy-four, eight percent. Seventy-five and up, twelve percent or more, and honestly at that point just run by feel.

Let me make that concrete, because percentages don’t mean much at a jog. Take a kid who runs eight-minute miles easy. At a seventy-two-degree dew point, that’s an eight percent adjustment. Eight percent of an eight-minute mile is about thirty-eight seconds. So her honest easy pace that morning is not eight flat. It’s closer to eight-forty. Same effort. Different number on the watch. If she forces eight flat, she’s not doing an easy run anymore, and I’ll come back to why that matters so much.

One exception, because somebody’s going to email me. The hot but dry day. If the air temperature is above eighty-five, put at least a three percent adjustment on it even if the dew point is low and the air feels dry, because that raw radiant heat still loads the body.

Now, I’m not asking you to do percentage math in your head at 6 a.m. with forty teenagers in front of you. I built a free heat pace calculator for exactly this. You put in today’s temperature and humidity, or the dew point if you’ve got it, and your normal pace, and it hands you the adjusted pace and flags the danger zone. It’s on the site, it’s free, and it’s in the show notes. Pair it with the rehydration calculator, which I’ll get to.

Better yet, teach the older kids the simplest version of all of this. On a hot day, run the effort, not the pace. If you’ve got heart rate monitors, even easier. Hold the easy zone, let the pace be whatever the pace is. It’ll land right about where that chart predicts, automatically.

Segment Four · Why Forcing the Pace Wrecks the Season

This is the segment I most want you to hear, because it’s where the season is actually won or lost. The title of this episode is not “running in the heat is uncomfortable.” It’s “without wrecking the season.” Here’s the wrecking part.

When your athlete forces her normal pace on a high dew point day, she doesn’t just have a hard run. She changes what the run is.

An easy aerobic run is supposed to stay easy and aerobic. That’s the whole job of the day. But on a sticky day, at that same pace, her heart rate and the strain on her body have climbed up into a completely different zone. So that easy run quietly turns into a threshold effort. Sometimes harder. The watch says easy. Her body is doing a hard workout.

Now run that forward across a whole summer. She’s piling up hard-day fatigue on days that were meant to be easy. She recovers worse. She stacks it up week after week. And she shows up to the first week of real season in October flat, or hurt, or just burned out, and nobody can figure out why, because on paper she ran all her mileage.

That’s the trap. That’s how a kid does everything you asked and arrives at the starting line worse for it. And here’s the rule of thumb I want burned into your brain. For every degree of dew point above sixty-five, knock off roughly five percent of your training load. At a seventy-two dew point, the same mileage is giving you something like thirty-five percent less effective, quality training than it would in October. Same number in the log. Very different stimulus.

So running by effort in the heat is not soft. Let me say that again for the tough-guy coaches. Backing off the pace in the heat is not coddling. It’s the correct training decision. The kids who get that are the ones who show up fresh in the fall, and the fresh team wins.

Segment Five · The Good News, Acclimatization

Now let me give you the hopeful part, because I’ve been beating you up with why heat is hard. Heat is a trainable stress. The body adapts, if you let it.

Give an athlete consistent, sensible exposure to heat, and she adapts in about ten to fourteen days, with most of the change happening in that first week. And the adaptations are real, measurable stuff. Her blood plasma volume expands, ten to twelve percent in the first several days. She starts sweating earlier and more, and her sweat gets more dilute so she holds onto more sodium. Her heart rate and her core temperature at the same effort both come down. In plain terms, the exact hot run that flattened her in early June feels manageable by late June, as long as she’s been running through it consistently.

Three things you need to know about that. One. The first few days feel the worst. That’s by design. Push through it sensibly and it improves fast.

Two. It runs in reverse. Stop training in the heat and you lose it in two to four weeks. So if you get a cool stretch, a couple of hot sessions a week will hold the adaptation.

Three, and this one is a hydration landmine. Getting acclimatized means she sweats more, not less. Her fluid and electrolyte needs go up as she gets fitter in the heat, not down. Which is the perfect setup for the next segment.

And this is exactly why the first truly hot day of the year is, statistically, when kids get hurt. Nobody’s adapted yet. So build your summer ramp gradually, in both mileage and intensity. Treat week one of summer practice as an acclimatization phase, not week one of a full training block. The kids who blow through week one like it’s midseason are the ones limping by week four.

Segment Six · Hydration, the Part Everyone Half-Knows

Everybody “knows” hydration matters. Almost nobody on your roster is actually doing it right. Let me give you the numbers.

Dehydration makes every single heat problem I’ve described worse. Lose two percent of body weight in fluid, and aerobic performance drops three to four percent. Push past four percent and the risk of real heat illness climbs fast.

Here’s what two percent actually looks like, because it’s less than people think. For a hundred-and-thirty-pound runner, two percent of body weight is about forty-two ounces of fluid. That’s three regular water bottles. On a humid July morning at ninety minutes of work, that is a completely normal loss. Not extreme. Normal. And completely preventable.

So here’s the plan. Three parts.

Before. Sixteen to twenty ounces of water in the couple of hours before practice. The check is simple. Urine should be pale yellow before they start. Dark yellow means they showed up already behind, and you can’t win the day from there.

During. Six to eight ounces every fifteen to twenty minutes. And do not let them run on thirst. Thirst lags behind the actual fluid deficit, especially in teenagers. If they’re thirsty, they’re already behind.

After. This is the one nobody does right. You have to replace more than you lost. About a hundred and twenty-five to a hundred and fifty percent of the deficit, sipped over two or three hours, because the body keeps losing fluid through urine and sweat while it cools down. Drink exactly what you lost and you don’t actually get back to even.

And how do you know what she lost? Weigh in before, weigh out after. Every pound gone is about sixteen ounces of fluid. I built a free rehydration calculator that does this math for you, and here’s the coaching gold in it. Have a kid weigh in and out after one hot session, just once, and show her the number. When a runner sees she lost three pounds of fluid in an hour, she never argues about the water bottle again. It teaches the lesson better than I ever could with a speech.

Quick note on water versus sports drink, because I get this from parents constantly. Under an hour, water’s fine. Over an hour, or in serious heat, she needs electrolytes, mainly sodium. And skip the high-sugar stuff. If it’s over about eight percent carbohydrate it actually sits in the stomach and slows everything down. If you see white salt stains on her hat or her shirt after a run, that kid is a salty sweater and needs the electrolytes more than most.

Segment Seven · The Safety Line You Do Not Cross

Now the serious part. Everything up to here has been about training smart. This is about keeping kids alive, and I’m not going to soften it.

Heat illness is a continuum, and the far end of it is exertional heat stroke, which is life-threatening and can escalate frighteningly fast. This is not a place to be casual or tough.

So here’s the framework. Two levels.

Modify the session when the dew point hits the severe band, sixty-five and up. When it’s the first hot stretch of the year and nobody’s acclimatized. Or when a hard workout you had planned lands on a brutal day. Modify means move the quality work to the coolest part of the day, cut the volume, add rest between reps, or just convert it to an easy effort and live to fight another day.

Cancel or fundamentally change the outdoor plan when the dew point climbs into the seventy-and-above range, especially with strong direct sun and dead-still air. That combination is the classic high-risk setup. On those days you go to a pool run, an early morning shift, or something indoors. You protect the fitness without rolling the dice.

And if the heat index is over a hundred and three, you cancel the hard outdoor workouts. No July workout is worth a heat emergency.

Now the part every adult at your practice needs to have memorized. The warning signs. Dizziness. Nausea. Headache. Confusion or any strange, off behavior. Stumbling or clumsiness. Goosebumps or chills on a hot day. Or a kid who was sweating hard and suddenly stops sweating.

And here’s the thing that makes all of that easier. Decide it in advance. Write a simple hot-weather policy before the season starts. The dew point where you modify, the dew point where you cancel, mandatory water breaks, kids run in groups and never solo, and a team culture where telling you “I feel off” is treated as smart, not weak. Because if your kids think stopping is a weakness, they will not stop. That culture is set by you, and it’s set long before the hot afternoon when you need it.

Segment Eight · Monday Morning

Let me hand you the practice plan. Here’s what you actually do this week.

One. Stop checking the temperature and the humidity. Check the dew point, near the time you’ll actually run.

Two. Run the mornings. Six to eight a.m. has the coolest air and usually the friendliest dew point of the day. Once the sun’s been up a couple hours, the pavement’s radiating heat and the deal gets worse. Find shade if you can. Shade can knock ten to fifteen degrees off the effective heat.

Three. Adjust the pace off the dew point, or better, coach effort and heart rate instead of pace. Post the dew point chart at practice so the kids see the slower number is the correct number, not a failure.

Four. Run the hydration plan. Pale yellow before, six to eight ounces every fifteen to twenty minutes during, and replace a hundred and fifty percent after. Do the weigh-in demo once and let the scale do your convincing.

Five. Respect week one. Cut volume and intensity twenty to thirty percent for the first week of real heat and let them acclimatize.

Six. Have your written heat policy. Know your modify line at a sixty-five dew point and your cancel line at seventy, and know the heat stroke signs cold.

Close

Let me bring it back to that freshman on the tempo run. The one who told me she was fine and that you just get used to it.

Here’s what I did. I pulled her aside, and I didn’t tell her to toughen up. I explained the physics. I told her the heat was making her body pay more for the same pace, that the number on her watch was a lie today, and that the tired legs were thermodynamics, not a lack of fitness. I taught her the dew point. I showed her the scale after practice.

And you know what happened? She stopped fighting the weather and started working with it. She ran the effort, she nailed her hydration, she got through the ugly first week, and she was one of the freshest kids on my line in October.

That’s the whole game. The heat is going to come. It’s here this week for a huge chunk of you. You don’t beat it and you don’t tough your way through it. You manage it, and you teach your kids to manage it, and you get to the starting line in the fall while everybody else is trying to figure out why they’re flat.

The heat pace calculator and the rehydration calculator are both free on the site, both linked in the show notes. Go put them in front of your athletes this week. And if you want the whole summer built this way, that’s the 22-Week Cross Country Season Blueprint.

I’m Coach Saltmarsh. Run the effort, not the pace. Keep it salty, and I’ll see you next week.