Homebrew
Happiness
Home
My Writing
#coaching
#creative writing
#culture
#mental health
#running
#science
#tech
#training
Coaching
Contact
About Me
My Strava
I acted like a heat amateur and dnf’d my long run - A Science Story
2025-09-04
My favorite running outfit right now is a pair of Janji leggings (POCKETS!!!) and a UV blocking long sleeve shirt from Ross. This specific outfit has taken me through all kinds of conditions and it’s—almost—always worked. It strikes a nice balance for cool mornings that turn into warm afternoons. I’ve always been someone who runs well in the heat. My PR in the two mile comes from a race I won in 95 degree heat in the St George desert. The track was an oven that day, but it worked for me. And it may very well have been a product of what I’ve felt most comfortable running in. While I wouldn’t consider myself a particularly self-conscious person—long sleeves and sweatshirts just <i>feel</i> better. I hear that’s a pretty common thing for trans people. Body-based gender dysphoria can sway fashion choice towards comfort and function. I definitely find myself drawn towards clothing that hides or de-emphasizes my body. So I’ve always preferred overdressing. That’s natural for me. And it was natural for me on Saturday—going to a new place, running with a new person, running further than I have in months—to opt for long sleeves and leggings. The outfit was a big mistake; a mistake that left me lying on the side of the trail making phone calls trying to find someone to come pick me up. Why it was a mistake dives into the fascinating world of heat science. So it’s science time! <h3>An Oversimplified Analysis of Physiological Thermodynamics</h3>  The body dispels heat in several ways. Here they are listed in order from most to least necessary: * Conduction - your skin touches something (like the air) and transfers the heat to it if the thing is cooler than skin temperature. * Limited by the temperature of the thing the skin touches. The colder the better. * Evaporation - sweat from your skin dissipates into water vapor. The hot sweat changing states of matter takes the heat with it. * Limited by access to open air that doesn’t currently have a bunch of water in it. High humidity or wet clothes can prevent evaporation. * Convection - Water or air moving over the skin grabs heat and takes the heat with it. The hot air or water is replaced by new cool air or water and the cycle continues. * Limited by air flow. Less air movement creates less convection. This is why treadmills or stationary bikes suck so much without a good fan. * Radiation - Your body emanates heat like a microwave. * Limited by the fact that your body doesn’t do very much of it. <h3>Why was my outfit such an awful choice?</h3> * Conduction - limited by wearing clothing across my whole body. The clothing heated up from the conduction and didn’t dissipate the heat very quickly. These clothes were meant for fall/winter weather so that’s technically a feature. * Evaporation - The weather Saturday was more humid than I’m used to and my shirt soaked through immediately. I was also wearing a pack and that DEFINITELY didn’t help. Evaporation essentially stopped being a thing for me once my shirt was wet. * Convection - No air exposed to my skin. No convection. * Radiation - Not effective enough at dissipating heat to make much difference. <h3>Why does it matter that I was so hot?</h3> The body is an awfully inefficient mechanical power generator. We’ll only ever use about a third of the energy we create within our muscles. In other words: we lose 70% of the energy we create during movement. You may “burn” 300kcals during your 5k but you only actually used 100kcals getting to the finish line. The other 200kcals became heat. Heat the body now has to do something with. To make matters worse—the body is picky about the thermostat. Once it hits 104 degrees, the brain will shut everything down and call it a day; and you better believe it will start complaining well before it’s quitting time. So the body has to offload a bunch of heat as quickly as possible just to stay alive. If we clog the final step of the process by trapping heat at the skin, all that heat stays in the muscle. Body temperature will rise, and then you’re toast. You slow down. Heat illness sets in. And you find yourself lying on the side of the trail calling around asking for someone to come rescue you. Don’t mess around with heat. <h3>Why is heat good then?</h3> Heat is also a miracle worker. The stimulus heat provides directly increases blood volume. More blood means more red blood cells. More red blood cells means more oxygen carrying capacity. And more oxygen in the blood means your electron transport chain can move faster and more efficiently. The electron transport chain is—in essence—the main limiter in aerobic energy production so if your electron transport chain is running smoothly <i>so are you</i>. Here’s a graphic I love:  There’s a lot of science mumbo jumbo on here but the key things for anyone to focus on are on that line second from the bottom. PV (plasma volume) goes up, BV goes up (blood volume), and RCM (number of red blood cells) goes up. More blood = better performance and better fitness. I won’t dive into the <i>how</i> of heat training in this article or the absolutely legendary role the kidneys play in this process.* Suffice it to say—when fully hydrated and with appropriate dosage and in the right context—heat can be a huge performance booster. Keep those training stimuli intentional, controlled, and safe. Don’t be a heat amateur. Good luck—stay cool—stay hydrated! YOU ARE AWESOME!! *I love the kidneys so much. They’re—in my humble opinion—the second smartest organ in our body after the brain. They do and control so much. They correct for our poor decision making constantly and it’s SO cool. References: SUU’s advanced exercise physiology class by Marcus Lawrence: <a href="https://drive.google.com/drive/folders/1Qdr6w02O5ZQId8xCVq3zwOOtSb9mLK0d?usp=sharing">Link to notes and slides</a><br> Figure 1 reference: <a href="https://www.louisvillelectures.org/the-ll-blog-1/heat-related-illness/lehto">Louisville Lectures by Victoria Roman and Elizabeth Lehto</a><br> Figure 2 reference: <a href="https://pmc.ncbi.nlm.nih.gov/articles/PMC7518763/?utm_source=chatgpt.com">The best academic article ever written on heat. Kissling Akerman and Cotter (2019)</a>
