The Real Dangers of Heat and Exercise: How to be Safe

At least in the Northern Hemisphere the heat of the summer is well and truly here and so is training season. The thing is this heat can be really dangerous on it’s own pair that with being outside and then add exercise and things can get really dangerous even bordering on deadly for some. I worry most about novice outdoor exercisers who might not yet realize they are overdoing it. You might also get the impression around here that it’s no big deal because well, I realized that I might give you that impression. I’m not a very at risk person for heat exhaustion and heat stroke, partially through genetics, partially through adaption and because of my age and size but we’ll get into that. I wanted to write a post both clearly pointing out where you can get into trouble and how to prevent it no matter who you are.

Who is at risk

On some level everyone is at risk. Given the right conditions anyone can actually die from the heat. The biggest group that expires in heat waves is the elderly because they tick a lot of boxes. Another group that’s really at risk are the very young but since they have parents constantly watching and caring for them they tend to do okay. So age is a factor, the older or younger you are the more at risk you are. Another factor is weight. While this isn’t politically correct this is a big one because it’s at least 2-fold. One is the fact that a larger body doesn’t cool as effectively as a thiner one. It’s a surface area to volume thing after all. The second factor is a larger body is physically harder to move through space. One youtube personal trainer I follow often makes the point that her heavy clients do a lot better than her very thin clients on her intake workout test. That’s because moving these bigger bodies leads to more muscle development. In the heat moving a bigger body puts you more at risk often without you even realizing it.

     Much of the really serious danger comes from dehydration when it comes to heat. So if your hydration status is challenged on a certain day because of sickness, drinking alcohol or just poor planning you might get into extra trouble. The fitter you are the less of an issue heat can be. A fit body is and efficient body and so it utilizes resources like water and cooling more effectively. The amount of sweating a person does is also really variable some sweat more or less all other variables equal. People who are not adapted to the heat  are also more likely to succumb to it. Think about it, chances are there is a whole lot of people that live somewhere a lot hotter than where you live. Those people can do things at temperatures that you can not. In fact when you think it’s too hot to go outdoors they might consider it sweater weather! Even heat warnings take this into account with in the same country. In the North of Canada heat warnings can be triggered at 20 c (68 f) here they are triggered at 30 c (86 f) but in Toronto it takes temperatures of 35 c (95 f) or more to trigger a warning. If you’re used to it you can get away with more.

Why I seem to be immune

Here’s the thing you might get the impression around here that the heat doesn’t effect me and the thing is it usually doesn’t. For one thing I seem to be built for it the other is I do take steps to stay safe. Let’s start with he obvious I’m pretty dang skinny that means moving in the heat I’m actually dosing less work out there. The next thing, I’m not really a big sweater, I mean I do sweat but not a lot, possibly even less than average. One thing that helps with that is my willingness to wear very little clothes. Next I’m pretty darn fit. I’m in at least 10k shape at least year round. A lot more in the heat of the summer and  due to training and the outdoor hard work nature of what I do. I also adapt early and hard to the conditions I’m outside pretty much every day, year round. So I have lots of opportunity to adapt and I do it early. I’m a person who also runs cold. In the evenings honey is usually sitting under the air conditioner shirt less and I’m wearing at least on sweater and long pants. Some of that is likely genetic too. Many years ago now I was working at a pool and the air conditioner was broken but for good reasons we decided to go ahead with the swim. As the temperature crept up to the 40’s the other young, fit lifeguards all had to leave for heat reasons and we did eventually call the swim when I was the only one left standing, some of that has to be genetic! I have had heat exhaustion at that job in the past and trust me it feels like you’ve been hit by a bus.

Take some time to smell the flowers when it’s hot!

Heat stroke vs heat exhaustion

Heat illnesses can be divided into two categories heat exhaustion and heat stroke. The first is not as serious but you don’t want to be running near cars when you are struck and the second can be deadly. Heat exhaustion is characterized by: heavy sweating, rapid pulse, dizziness, fatigue, cool, moist skin with goose bumps when in the heat, muscle cramps, nausea and headache. Where as someone with heat stoke has a body temperature over 104 degrees and has usually stopped sweating at this point. Both are obviously dangerous but the second is deadly. More Americans die from heat each year than tornadoes, hurricanes, flooding, lightning or any other weather event combined. 

You don’t necessarily get heat exhaustion before heat stoke but many do and both can come on gradually or suddenly. Here’s the thing though exercising is a risk for both and if you are exercising in the heat you can expect: heavy sweating, an elevated pulse, fatigue and if you’re going really hard maybe some dizziness, nausea and a headache but that’s a sign you are overdoing it and probably under hydrated. So it’s easy to dismiss the symptoms and get yourself into trouble. Here’s what you can do to prevent issues with the heat this summer.


Consistency is key in any workout schedule for a variety of reasons one of which is dealing with the heat (and the cold because that is coming…) As much as you might want to skip the in between weather and jump in with both feet once it gets warm, don’t. Instead workout in the heat as you will later two or three times a week as the weather warms up. Your body adapts quickly to the heat in a few days to a week each time temperatures climb. Saying consistent can keep you safe here!

I workout outside physically every day so by the time the heat hits I’m well adapted but we take it seriously at work too. The first few days of intense heat we take it easy, stay hydrated on purpose and often call the day after a couple of hot hours. I also run a least once outdoors every single week outdoors year round, so I have this category seriously covered.

Hydration and cooling

The best thing you can do is to hydrate with cold fluids before during and after with cold water. Keep in mind though not to guzzle a lot of really cold water while you’re out there which can make you lose consciousness. A general rule of thumb is to drink WAY more water than you think you need too. Sports drinks can be a part of that equation but they are no magic bullet when it comes to hydration or electrolytes. A great old life guard tip to bring you around is to add a pinch of salt. Too much and you’ll throw up but add enough that it doesn’t taste salty but rather just a bit different and it will really make you feel better when you do border on exhaustion. Another tip science has found drinking a slushy before your workout can let you go harder for longer compared to cold water. Also take mostly ice in your first bottle and freeze the second solid so it stays cold

Take it indoors or change your workout

I am way more likely to hit the treadmill due to cold than snow but know that’s always an option. Running early in the morning or later at night is a great idea but the morning is usually cooler. Check out this post on how to get up early and workout. Also run by perceived effort and let go of pace. In other words it should feel as tough as your regular workouts of that type regardless of pace. If all else fails find a treadmill with air conditioning or switch it up for a swim!

Get less of the right gear

Let go of modesty and bare some more skin. The best way your body cools itself is to evaporate sweat from your skin. I opt for a sports bra and shorts in anything really over 20 degrees. Realize that the person that cares the most about your body is you. On a very warm day people are only looking because you literally look hot! Anything else you wear should be a technical sweat wicking fabric before. Even those fabrics have a range of how well they perform. Save your best ones for the hottest days. Also consider wearing a hat to keep the sun from beating down on you.

Other tips for warm weather running here

At the first sign of distress get out of the heat or at least into the shade and stop your workout. Call someone for a pick up and do what you need to to cool down. On really hot days I often dive into the ocean at the end of my run. You also might catch me doing an air out the armpits style of move which does make you feel cooler. What are your top tips for surviving a heat wave?

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