If you can't take the heat..

 ..then you might want to evaluate the adaptation strategies you're using.

Why am I talking about heat management when autumn is upon us?
It may be more timely than you think.

There is a large body of evidence to support what every runner (and cyclist, and any other person who does anything even marginally athletic outdoors at summer's scorching heights) knows: athletic performance suffers in high heat. We can, however, somewhat mitigate that performance drop through careful application of adaptation strategies.

I've previously talked about in-competition heat management, so we're just going to leave that out of today's discussion. This is more for folks who might want to do a destination race at some point, or just kick start their heat training in spring to be ready for a big race. Full adaptation takes anywhere from a couple of weeks to multiple years (depending on the type and depth of effect we're talking about), so if the 14 day forecast for Around the Bay or Sulphur Springs predicts a heatwave and you want to limit your suffering, this may have some value for you.

If you're just here for some pretty trail pics, that's fine, too.

There are two different types of adaptation available to us mortals: 

1) Acclimatization: This is the natural process of adapting to a warm environment. Easily achieved in summer by just going out and doing your best to slog through runs (or other types of exercise) on hot, sunny afternoons.

2) Acclimation: This is intended to produce the same sorts of adaptations, but through artificial means of input. Examples include sauna use, overdressing for runs, or use of a treadmill in a heated room.

In both cases, the body is expected to respond to increased core and skin temperatures by increasing sweat rate, reducing time to onset of sweating, increasing skin vasodilation (the expansion of surface blood vessels to increase blood flow, essentially turning your skin into something like the fins on a radiator), reducing sweat electrolyte concentration, increasing cardiovascular stability, and reducing your internal body temperature responses and rate of perceived exertion. With acclimatization, it happens organically - like getting a tan after being out in the sun. With acclimation, you're attempting to produce the same results through other means; equivalent to using a tanning bed.

Except don't ever use a tanning bed. Just don't.

Before we continue, let me emphasize: I am not a exercise physiologist. I sort of have access to a lab, but not one that has any bearing on the concepts I'm about to put forth. That's why this is Seems Like Science™ and not ACTUAL science. Anecdotes are not data, but they're what I've got, so I'm gonna throw down some theorizing based on n=1 here.

I ran around a lot in the high heat and humidity this past summer, often at the hottest, grossest part of the day. I have a pretty solid handle on what that feels like, and how crushing it can be. No, really - I thought my fitness had taken a horrible dive because there were days when I couldn't make it a damn kilometer without having to stop to catch my breath, or walk a bit. It was awful. 

More recent weather has shown I'm not quite as pathetically out of shape as I'd feared

So here's the thing: because I run down to the Cambridge Farmers' Market most Saturday mornings, that means I'm out on the trail for over an hour during that time of day when it's going from positively frosty out to a much more human-friendly temperature. The sun can also make it feel much warmer out than the thermometer would suggest, and because I am a bit of a weenie I often end up hopelessly overdressed for the conditions.

Case in point: it was 1c/33f when I left the house, and 10c/50f when I got to the market

Here's the thing, though: despite being a sweaty mess inside my too-warm clothing, I've noticed I don't experience anywhere near the performance impairment I was fighting in the summer heat. It could partly be because I'm still heat adapted, but then when the thermometer suddenly rises (as it is sporadically wont to do in autumn in Ontario), there I am panting and gasping again.

So what's the deal? I have a theory, formulated on one of those desperately-trying-to-zip-down-collar-and-push-up-sleeves runs to the market: what if it has something to do with the temperature of the air you're breathing in? We can give this a (hasty and uncreative) name: the Respiratory Temperature Theory of heat adaptation, or just RTT because I'm heckin lazy.

Fear not: I'll continue to punctuate my crackpottedness with more trail porn.

If this is anywhere near accurate, this has significant implications for some of the heat acclimation strategies traditionally used by runners in colder climates before heading to races in warmer environments, like someone from Canada doing a wintertime race while on vacation in Florida or Mexico.

If RTT is correct, overdressing for runs - like trotting around in a parka on a mild autumn day - will not help you adapt.

Sauna use has gained an increasing body of peer-reviewed research (you know - actual science instead of just some weirdo blathering on the interwebz) showing effectiveness in heat acclimation for exercise. However, the studies I've seen on trained individuals (like this one, and this one) have used traditional types of saunas, whether humid or dry. In either case, they have used a type that heats the actual air the athletes are breathing. Infrared saunas, though - which are much more economical to both purchase and operate, and thus quite attractive to someone looking to use post-exercise sauna treatment to trigger heat adaptations - would not be effective if RTT is correct.

Stay with me here..

You see, infrared saunas (and heaters, for that matter) use infrared radiation to produce heat. This radiation only warms things that absorb it, like your skin, or other objects in the room with the heater. It doesn't actually warm the air, which is why you might feel comfortable in a room with a quartz infrared heater turned on, but will feel cold again as soon as you turn it off. 

If your lungs (or nasal passages, or esophagus) have some kind of receptors that allow them to sense air temperature and transmit that information to the brain which results in higher perceived rate of exertion, higher heart rate, and general decrease in performance condition, the only way to adapt to the heat would be to repeatedly expose your lungs to warmed air during exercise.

If RTT is correct, then the best methods to achieve heat acclimation would be the use of a treadmill in a warmed room, or the use of a traditional (i.e.: non-infrared) type of sauna. 

It's also possible that humidity plays a greater role in the decline in performance seen in hot climates, in which case the use of a traditional sauna or steam room would be the best method to trigger adaptations. Maybe put a big bowl of freshly boiled water on the console of a treadmill as a low-budget alternative?

Yeah ok - like I'm going to use a treadmill!

There's also the small detail that solar radiation can have a huge impact on athletic performance, as shown in this study on trained cyclists. So, it's possible that my little theory is worth about as much as the paper it's printed on.

Keeping in mind it's only on the internet.

If you figure I'm on to something, feel free to do some experimentation for yourself. If not, well...maybe we'll just leave things to the actual exercise physiologists next time.

EDIT: especially since I've 100% failed to realize that cooler air is denser and more oxygen-laden, which means of course there's a correlation between ambient air temperature and performance regardless of adaptation. I'll sit down, now.

Stay cool out there!