Things We Don't Consider That Can Make Us Overheat

This morning, I was getting ready to go about my day in New York. My building has building-controlled heating, and someone didn’t get the memo that on a 72-degree day, we don’t exactly need the same winter-level heating that we used when it was 2 degrees Fahrenheit. No matter, I had my White Sands hooded henley. So I put it on. And uh-oh… I was still warm at first. Wait, what? We’ve tested this and it’s done fantastic above 100 degrees. So why was I warm now? Did this undermine the product development that we've put into our hooded henley?

Then I realized that there were several factors at play. I had on pretty tight jeans, and this was the first actually warm day of the spring. That got me thinking about all the other things that we don’t really think about that often when it comes to heat dissipation. I made a list, did some research, and drafted some thoughts below (btw at the time of writing 4 hours later, I’m feeling much cooler in the same White Sands shirt). 

YOUR PANTS

Almost everyone misses this. How often do we carefully select a breathable shirt and then, without a second’s consideration, throw on heavy denim or chinos. Your legs present a huge surface area, and thick, tightly-woven material down there can pretty much cancel out all the good your shirt is doing. Swap your jeans for something lighter on a  hot day, like, oh I don’t know… the Joshua Tree pants by Terlingua Threads. Perfect product placement. Buzzfeed would be jealous (btw bet you haven't thought of them in a while).

TIGHT-FITTING ANYTHING

Anything that’s tight. Wherever fabric is pressed right against your skin, air can’t move. Think a snug waistband, compression underwear, tight socks. Our bodies cool down in part by convection - warm air rising and cooler air taking its place. Tight clothes eliminate those small air pockets which make that happen. Which is why all of Terlingua Threads gear is meant to be relaxed-fit and flowy. 

YOUR BACKPACK

If you’re on a hike or commute around by walking like in New York (or any city, really) this is unavoidable, but it’s good to understand. A backpack covers the whole of your upper back, and that's one of the places your body sweats most efficiently. It forms a sealed, warm, damp area exactly where you need ventilation. You’re not going to stop carrying your backpack, but realizing your back isn't cooling down means the ventilation in the rest of your clothing is even more important. If your back can’t breathe, your shoulders and armpits are doing all the work. That’s why our VentMap placement developed with the aid of internal medicine doctors and outdoor guides was so critical – we map where the body disperses heat for our button-up shirts. But even with our vent placement, a backpack will still reduce surface area that your skin comes into contact with air. 

NON-VENTILATING HATS

Protecting your head from the sun is sensible. However, a typical baseball cap without mesh sections traps heat on top of your head - and the top of your head is a major heat-loss area. You’re blocking UV rays (that’s good) whilst simultaneously blocking a place where your body gets rid of heat (less good). Look for hats with mesh sides or holes in the crown. There’s a balance between sun protection and letting heat out of your scalp, and most hats completely ignore it.

NECK GAITERS AND BUFFS

Your neck has blood vessels very close to the surface of the skin, making it a really effective place for your body to lose heat. A tube of fabric wrapped around it, even if it's thin, acts as insulation. So, if you’re wearing a gaiter for UV protection on a 95-degree hike, you’re protecting your skin but also limiting your body’s ability to get rid of heat from one of its most efficient heat-dumping spots. There isn’t a perfect solution, but being aware of the trade-off will help you decide when to pull it up and when to let your neck get some air.

HEADPHONES

Don’t get me wrong, I love my AirPods Max (still rocking the originals from 2019 with the Lightning connector). They’re definitely needed in a noisy co-working space. But over-ear headphones make sealed, insulated pockets around your ears. Your ears are full of blood vessels and release heat (that’s why all our favorite hot-weather mammals have adorably large ears). On a warm journey to work or a summer run, those padded earcups are acting as little insulators on two of your body’s ‘radiators’. They won’t be the deciding factor on their own, but combined with a backpack, a hat and a warm day, they add up.

CHEMICAL LOTIONS

Chemical sunscreens and heavy body lotions. Chemical UV filters (avobenzone, oxybenzone, octinoxate) absorb UV rays and turn them into heat which is then released at the skin’s surface. Mineral sunscreens (zinc oxide, titanium dioxide) reflect UV rays, which is why we lean towards using them personally. The difference in how they feel on a hot day is obvious, particularly when you've applied them to large areas like your arms and chest. And piling on thick body lotion before sunscreen can make this worse by reducing how easily sweat evaporates over a large area of skin.

Now, one thing we’ll keep saying over and over and over: SUNSCREEN IS ESSENTIAL. Our clothing, while UV protecting, is never meant to be a replacement for sunscreen, and it pisses us off when some brands say you can ditch the sunscreen by buying their clothes. We will never dole out bad medical advice as a kitschy way to try to bamboozle people into buying more product. Terlingua Threads is meant to be a part of your arsenal along with sunscreen, proper hydration, and common sense. 

LARGE MEALS

After a big feast, your body sends blood to the stomach to deal with the food - that's blood that isn't going to your skin to help you cool down. Your body is then doing two important things at once: digesting and trying to get rid of heat, and they're battling for resources.  A heavy meal before a hot afternoon of hiking creates this internal struggle. Protein is particularly bad; your body uses around 20-30% of the calories from protein just to digest it (compared to 5-10% for carbs). A steak makes a lot more heat during digestion than a bowl of rice and on a hot day, that extra heat really adds up. 

CAFFEINE AND ALCOHOL

Coffee and beer aren’t helping either. Caffeine boosts your internal temperature and also makes you urinate more, so you have less liquid to sweat. That morning coffee before a summer hike is a little way to undermine yourself, and most people don't even consider it. Alcohol is even worse. It makes your blood vessels widen (that warm feeling) and then causes dehydration. That initial warmth on your skin is then followed by reduced sweating as your fluid levels go down, plus it’s also a diuretic.  That beer after a hike at the campsite, while it may be absolutely well-deserved, will likely work against your body's cooling efforts. You don't have to give up either, of course, but if you're unexpectedly warm on a fairly mild day, they could be the hidden issue.

MEDICATIONS

A 2020 study in PLOS ONE showed several common drugs get in the way of your body sensing and dealing with heat. Antihistamines (Benadryl, Zyrtec) lessen sweating.  ADHD meds (Adderall, Ritalin) make your internal temperature rise. SSRIs and other antidepressants can generally mess up how you regulate temperature. Blood pressure meds - ACE inhibitors and beta-blockers - can suppress your thirst or cut down on sweating. Even common cold remedies like pseudoephedrine (a decongestant) have a stimulating effect that creates extra body heat. Importantly, and we must be very clear, don't stop taking anything your doctor has prescribed because of something you read online. Now, we aren't doctors and this isn't medical advice, and talk to your doctors about the side effects of what you’re taking (side note: I’m realizing how by typing this, I’m at risk of sounding like a prescription drug commercial – can you believe that those are actually legal in the US? But anyways). But if you're on any of those and you find you're warmer than you used to be, or heat bothers you more now, bring it up with your doctor. Being aware of this is important, especially when you're out in hot weather. 

SEASONAL ACCLIMATIZATION

And finally, the first warm day of the season (what's called seasonal acclimatization). This is one of the most important thing on this list, and probably has the most to do with why I was so uncomfortable in my apartment this morning. Your body needs about ten to fourteen days of being consistently warm to adjust its cooling system. During that time, you'll start to sweat later, sweat less effectively, and your blood vessels will be slower to widen and bring heat to the surface. This adjustment is called heat acclimatization and is a well-researched physiological process. The result is that 75 degrees in late March and 75 degrees in mid-July don't feel the same to your body. It’s kind of like how when winter first hits, the same temperature that you’d need layers on layers for, you can get by with a light jacket when spring comes knocking. 

This is why the first heatwave of summer always surprises people. It's also why experienced hikers and guides take it easy for the first few hot days of the season – we know our bodies need to get used to the heat.  Anyways, stay safe, take it easy, and please let us know if you have any questions or ideas.