Tag Archives: overtraining

Endurance: the ultimate test of physiology.

For a beginner runner to get into running because in 6-12 months they want to run an ultra-endurance race (or even a marathon) is—to put it mildly—folly.

There’s a reason the marathon is the final event in the Olympics: It’s by far the hardest. A recent The New Yorker article reports on one athlete trying to describe the experience of running a 2:10 marathon: “You feel like you will die. No, actually die.”

There are fundamental differences between the endurance sports and the power sports. Oftentimes, when discussing these differences, people think about what gives an athlete a competitive edge: for power sports, it’s higher concentrations of Type I muscle fibers. For endurance sports, it’s more mitochondria, and a greater oxygen carrying capacity.

This is important, but it’s not what I’m talking about. I’m talking about understanding the endurance sports by attempting to discuss what “endurance” is—not human endurance, or endurance at sports, but rather what “endurance” means in a fundamental sense. And for that, I find it best to discuss extremes.

Take a power sport: the 100 meter sprints, for example. Usain Bolt is a phenomenal athlete. There’s no question about it. And there’s no question that there’s a certain glory to be had in being the fastest human being on the planet—glory that is simply not available to the marathoner. Let’s set that aside. What would have to happen for Bolt to be unable to continue competing?  In other words, what would “catastrophic system failure” mean for Bolt?

My answer is: an ACL injury, or a torn hamstring, probably. In other words, something breaks.

Now let’s look at the marathon. Rarely does something break in that way in the endurance sports. There’s plenty of microdamage—achilles tendinitis, stress fractures, chronic fatigue, etc. But when something breaks, truly breaks to a point where the person cannot compete (in the “catastrophic system failure” sense discussed above), what does that look like? It’s typically the entire system that fails. Take a gander at a list (compiled off the top of my head) of the quintessential ailments you see in a marathon:

  • Extreme dehydration
  • EAH/EAHE (Exercise Associated Hyponatremia/Hyponatremic Encephalopathy)
  • Heart attack
  • Kidney failure
  • Heatstroke
  • Respiratory infections

What these issues all have in common is that they’re systemic failures—they’re what happens when the body as a whole, rather than a specific part (say, the hamstring) can’t cope with the event. In other words, they’re what you get when the body starts to come apart at the seams.

The best way to think of this difference is that when you bust a hamstring (or even break your spine in certain places) you can still use your body as a whole except for the part you broke. But when you get any of the illnesses that typically occur during a marathon, it’s the entire body that is put out of commission—sometimes permanently.

To put it simply, we can think of speed and power as a question of how powerful the body is. And while speed and power have tons of importance in the endurance sports, we can say that endurance is primarily a question of how good the body is at holding itself together. In other words, endurance is a test of the body’s fundamental integrity: of how much stress can you subject it to for how long without any substantial collapses in any critical processes.

And this is the main difference between the endurance and the power sports. In the power sports, the body has to be very, well, powerful, but it doesn’t have to be all that good at holding itself together—at least not in ways that relate to the ailments described above. After all, the power sports only ask the body to perform for a few moments: it stops before it becomes dehydrated, or before enough lactate builds up that the kidneys fail, or before the lungs become stressed enough that they become susceptible to infection (etcetera, etcetera).

But that’s not the case in the endurance sports. The body is going to be in activity for a very long time. If any of its systems (respiratory system, cardiovascular system, etc.) are working at different rates, some of those systems are going to get tired first. This is a problem: those systems were only active in the first place is because they were providing a critical service to the body’s endurance performance.

When one of those systems fails, some critical process associated with it also stops. If the body continues activity in this state, critical processes start falling like dominoes. And the body starts coming apart at the seams.

It’s not that endurance sport are “better” or “more of a sport” than power sports. But it is the case that being highly successful at an endurance sport takes much more time, much more consistency, and much more athletic maturity than to be highly successful at a power sport. This is why, for example, it is not uncommon to see 19 and 20 year old athletes competing in power sports at the Olympic level—the 400m, the 1500m, etc.

It’s usually those very same athletes who, 10 or 15 years later, are running marathons. Once their athletic career was already taking off, it took their body an additional 10 to 15 years to be physiologically organized and cohesive enough to run a marathon.

On the other hand, any athlete who is seriously contending for a medal at an endurance sport at 20 years of age, is a unicorn. Either they’re already so athletically mature that they’ll have a wildly successful career ahead of them, or they have already pushed themselves so far, so fast, that decades of chronic illness and overtraining are already on the horizon.

High-intensity fitness culture, explained in systems: Physiology, evolution, overtraining in ultrarunners, and what it means for the rest of us.

In the modern approach to training and fitness, the idea that you should (or need to) train at a low intensity is utterly neglected. This neglect is a huge problem. It benefits the few, and harms the many. And even when this philosophy works, it only does so up to a point.

A recent article in Outside Magazine bit into this issue with great abandon. The Outside article discussed the extreme example: Overtraining Syndrome (OTS) in ultrarunners. Many elite ultrarunners have become seriously overtrained, finding that their legendary competitive and running ability evaporates almost overnight. And we see this sort of thing across the board: in crossfitters who get exertional rhabdo; in recreational runners that start too hard. But why does this happen?

Our present fitness culture has an extremely damaging “more is better” and “no pain, no gain” mentality. If your favorite sport is HIIT or CrossFit, you’re prompted to increase the intensity, to “feel the burn,” and to “not feel your legs after leg day.” You name it, it’s out there. If your favorite sport is running, everything around you tells you to collect miles like they were baseball cards—the more the better.

The problem is this: whether you’re an elite ultraunner or someone who is just looking to shed some pounds, the amount (or type) of training that society pushes you towards typically means a lot of stress. It’s not that you won’t get quick results with that high-intensity training program (or by going out and clocking as many miles as you can). It’s that in doing this, a majority of people cross a stress threshold beyond which it’s impossible to keep these gains. It happens to Joe Smith at the gym, and it happens to the ultrarunner.

But in order to understand why it happens (and why you can’t cheat your way around it) we have to discuss a critically important biological system known as the Hypothalamic-Pituitary-Adrenal, or HPA axis.

The HPA axis is the system that creates the autonomic stress response (ASR)—which kicks up the organism’s stress levels (think: alertness) in order to survive a challenge to its existence. Let’s put this in a real-world example: alertness alone isn’t enough for an antelope to escape a lioness. There are two more components to ASR: First, the antelope’s heart rate has to go through the roof in order to bring a high volume of blood to the muscles. Second, the antelope’s anaerobic energy system—which burns sugar without the presence of oxygen, kicks in.

There’s another energy system available to the antelope: the aerobic energy system. It burns a much more plentiful resource—fats—but it takes some time. The fats have to be broken down into sugar, transported through the bloodstream to the muscle fibers, and combined with oxygen inside the mitochondria, before they can be converted into energy. Typically, it takes the aerobic system 15 minutes to get to full burn. But the antelope doesn’t have 15 minutes. It doesn’t even have a few seconds for the initial gulp of oxygen to reach the muscles through the bloodstream. There’s a lioness charging towards it at 40 mph. It needs energy now.

lion hunt
Or towards a water buffalo.

Stress, a high heart rate, and the anaerobic system are hardwired together in every animal. This wiring has to be absolutely reliable. If it wasn’t—if, given certain conditions, you could get a high heart rate and stress but no spike in anaerobic activity—you will die. As far as your body is concerned, in a “real-world scenario” the price for not having these three things occur together every time, with utter certainty, is death.

That’s what your body is thinking—thanks to your HPA axis—every time you get too stressed. Your HPA axis has to assume that there’s an imminent threat to your life, and make all of your internal systems react accordingly. If not, you will die.

The anaerobic system takes over to ensure the immediate survival of the organism. It doesn’t just happen to burn the fuel we use in the short term (sugar). We are wired so that when our bodies are thinking and acting in the short-term (that is, prioritizing escape from a threat over long-term health) we use the anaerobic system.

On the other hand, when our bodies are behaving with the long-term in mind, we use the aerobic system. In the long-term, it doesn’t matter if all the energy isn’t available right now—we’re not running away from anything. On top of that, we have fats, which is a more reliable and plentiful energy source. Sure, it takes a little bit more time to get energy from fats than from sugar, but time is something we have.

But that’s not all: there are reasons to NOT use the anaerobic system in the long-term. Burning sugar without the presence of oxygen wears down the engine: it accumulates protons—hydrogen ions (H+)—which cause the body’s pH to fall, becoming more acidic. (The idea that lactate is the culprit of muscle acidification is a misconception: the presence of lactate predicts, rather than causes, proton-based acidosis in the body).

In the short-term, the antelope’s body doesn’t care about its pH balance. If it doesn’t move, NOW, that lioness will take it down. The temporary acidification of the body is a small price to pay for escape. If everything goes as planned, 45 seconds from now, the antelope will have a chance to calm down. Its stress levels will drop, it’s heart rate will slow down, and a powerful aerobic base will kick in and all the lactate will get churned through the muscle mitochondria and converted into more energy. The proton build-up that happened during the chase will be quickly negated. In that process, a final acidic by-product will come out in a form that the body is designed to quickly and competently expel: CO2.

As soon as the body’s short-term survival has been secured, and it starts thinking in the long-term, it uses its aerobic system.

But if you are under chronic stress, your body never gets a chance to think in the long-term. Remember that stress, an elevated heart rate, and anaerobic function cannot be untied. If you are under stress all the time (even if it’s work stress), you’ll have at least some anaerobic function. Your body will be burning more sugar and less fat. As you use the aerobic system less and less, it will grow less inclined (and less capable) of fueling your daily activities with fat. You’ll have to rely on dietary sugar to keep your energy levels up. You’ll burn even less fat. You’ll slowly and steadily gain weight. But your body will also have a higher proton concentration than it should. It’ll remain more acidic. You’ll wear it down, putting yourself at risk of chronic disease.

Just look at how this snowballs. The media (and your peers) are kind enough to pelt you with exercise programs that promise quick, short-term gains! You can see where this is going. You’re piling acute stress on top of chronic stress. Your problem wasn’t the excess fat itself: it was that your long-term energy system—the aerobic system—was compromised. And those quick, short-term gains that you’re promised? You might get them, but at the cost of keeping them.

Yet again, you’re using the short-term energy system. Yet again, you’re training your body to think in the short-term. The energy system that is responsible for your body’s long-term upkeep is incompetent. By definition, you’ll be unable to maintain that level of activity in the long-term. You’ll lose those short-term gains.


The problem isn’t that you’re flaky, or that you’re not an athletic person, or that you’re not determined. No amount of discipline or determination will be able to overcome the fundamental problem: that you trained for the short-term instead of the long-term.

The Tales of Forgotten Subsystems, part III: aerobic respiration, a.k.a The Krebs Cycle.

What if I told you that by running at a lower intensity, you could boost your running efficiency by 600%?

You’d think I was lying.

Well, I’m not. That’s exactly what happens when we run at the right intensity. When we’re burning sugars anaerobically, the sugar only gets partially processed by the cell, and out comes lactate. But when we burn them aerobically, that lactate goes through another process: The Krebs Cycle.

Continue reading The Tales of Forgotten Subsystems, part III: aerobic respiration, a.k.a The Krebs Cycle.

Workouts don’t develop the body. Resting after them does.

I often hear fellow athletes and fitness enthusiasts bemoan that they missed a workout.

There’s a lot of reasons people have this attitude. Maybe someone’s counting calories, and they are too tired to burn their allotted amount today. Maybe they have a strict training plan, and they feel obliged to stick to it. Maybe someone’s worried that if they stop they’ll never go back because they’ve hated the workouts, hated the nutrition, and only do it for the looks—or the speed.

You can’t “miss” a day of training, especially if you’ve been training so much (or eating so little) that the reason you missed training today is because you’re exhausted. Continue reading Workouts don’t develop the body. Resting after them does.