Here, I begin to answer a comment from this post, by Liliana Gutierrez Mariscal:

What makes running difficult for me?

Running in the heat

No matter what you do, it will be more difficult to run in the heat than in cool weather. But if you do take the time and trouble to run in the heat, it’ll really be worth your while.

I’ll devote another blog post to a very innovative idea that’s been put forth by a wealth of authors and scientists: the idea that we evolved into what we are now by chasing down four-legged animals in the heat of the african desert, (in other words, that we are desert endurance runners). But let’s not be tricked into thinking that achieving that level of expression will be an easy task.

Suppose we truly did evolve for the purpose of being runners, and more importantly, thanks to that activity. That being the case, we can make the argument that, running in hot weather in particular constitutes a very important part of the physical and physiological (and no doubt cognitive and emotional) expression of a human being.

Perhaps one of our most natural forms of expression (if not the most natural) is to run in the heat.

This argument comes from an evolutionary-systemic point of view. If you use a particular system for the very activity that it was developed to do in the first place (by first making it capable of operating at that level), then that system is very likely to manifest functions (or an efficiency of function) that it can’t express by performing any other activity.

Ultrarunning—the sport of putting the body through an irresponsible amount of miles—may tap into that level of expression. We already know that people sign up to run across the Sahara Desert, Death Valley, or to do back-to-back marathons in the desert summer as is the case with the Comrades Marathon.

But you don’t need to look that far for some idea that running was not created equal to other sports: Answer in the comments if you’d ever heard of a “golfer’s high,” or a “cyclist’s high.” It’s not that these cognitive states don’t happen in those sports. But the associations between running and favorable cognitive states are that much higher. They are so high, in fact (or so I argue), that people still sign up by the hundreds of thousands to run 26.2 miles despite the near-certainty that they will end the day with a significant injury.

Why do we still do it? As Christopher McDougall argues: it’s because we were born for it.

Those are the ultimate reasons for why you should run in the heat.

But I’ll give you a more proximate reason: you can make bigger gains in performance. I’m going to paraphrase a chapter-long argument in Tim Noakes’ book Waterlogged: The Serious Problem of Overhydration in Endurance Sports.

There are two important numbers in this story: 98.6° Fahrenheit and 104° Fahrenheit.

The first number, 98.6°, is of course, our normal core temperature. 104° is the temperature at which the body’s functioning becomes compromised. (This is a severe emergency).

What this means is that there are still, say, 2½ degrees of “give” between normal core temperature and the temperature at which things start getting too close to the danger zone (which starts at around 101º).

Take your typical runner stepping out into 100º heat for the first time: the body feels the heat and decides that no way is it going to let core temperature rise. It’s not accustomed to that environment—and more importantly, it doesn’t have a sweating system powerful enough to bring core temperature down, in case it needs to.

The cooling system of this average runner is fighting the environment heroically, struggling for every single tenth of a degree. That has a huge metabolic cost: the cooling systems go into overdrive, and the runner experiences fatigue in order to force a reduction in activity. Maintaining core temperature at a level that the body is comfortable with has become the most important thing—far more important than athletic performance.

But as that runner continues to train in the heat, the body begins to adapt over time: its sweating mechanism becomes more powerful, its able to more effectively circulate blood from the core to the skin—and furthermore, it knows that it’s still got those 2½ degrees of “give” between normal core temperature and the 101°, where its really beginning to skirt close to the danger zone. The runner experiences incrementally less and less fatigue; running becomes easier and easier.

As sweating system becomes more powerful, the body gives itself a little bit of rope. It’s getting used to that heat, so it lets core temperature rise a tenth of a degree, then another, and another. This isn’t a problem—it’s still in the safe zone.

What’s happening? It no longer has to fight the environment to cool those three-tenths of a degree.

In other words, the body developed a more powerful cooling system, and yet, because it developed that system, it no longer needs to use it that much!

Becoming accustomed to the heat lets you increase your level of performance in two ways: you can keep exercising at a higher core temperature, and with a more powerful sweating system. Suppose you increase your metabolic rate to tax the sweating system (which has now become more powerful) just as much as you used to tax it when you had only just started running in the heat: now you’ll be running at a much greater speed—and none of this has to do with your muscle power.

This brings us back to the argument that I was making earlier: by running in the heat, you can manifest physiological functions (heat tolerance) and psychological functions (lessened fatigue) that can’t be manifested under any other conditions.

The argument I make in this post is very similar to the argument I made in yesterday’s blog post. Just like having stronger muscles makes you a faster and safer runner at the same time, having a stronger sweating system does two things, instead of just one.

All this said, training in the heat means that we’re going to be playing with dangerous forces. Too much heat really will kill us. If we do choose to train that way, let’s do so with humility and care.

This will become a recurring topic. Soon, I’ll post a few exercises and training ideas that we can use to safely develop our heat tolerance. Also, I’ll post about the physiological aspects of the human body, that make us such good heat runners.

Remember, even though running in the heat might be really difficult, in a very deep way, it is what you do. If you gain that ability, you probably won’t regret it.

Happy running!