Tag Archives: athletics

Understanding the gears of the human drivetrain: energy systems and some of their training and racing applications.

Not long ago, I read an article from Outside Magazine which mentioned an elite cyclist who eschews heart rate monitoring during training in favor of power meters because “power is objective.” While I like power meters and I think they are an important tool in our (presumably much larger) athletic toolbox, I take issue with this view.

While a power meter tells us exactly how much power the body is putting out, it doesn’t tell us a lot about how the body is arranging for that power to be produced. That’s a problem.

The body has 2 main energy systems, both of which are used in varying amounts during a bout of activity: a capability to create energy by breaking down glucose, or sugar (call this “LO gear”—producing the low-end torque needed for power and acceleration) and a capability to create energy from lipids, or fat (call this “HI gear”—producing the high-end torque necessary for endurance). LO and HI gear can be subdivided into more energy systems—ATP-PC, anaerobic glycolysis, glucose oxidation, fat oxidation, and ketosis—but I believe that the beginner (particularly the beginner distance runner) should first master the distinction between fat and sugar usage, and how to apply it concretely to training and racing.

As I’ve discussed before, our heart rate is hardwired to our stress levels (a.k.a. the intensity at which our body is operating or expects to operate), and therefore to whether we are breaking down sugar or breaking down fats—in other words, which gear we are using at any given time.

The higher our heart rate, the more we are using the LO gear necessary to produce lots of power. The lower our heart rate, the more we are utilizing the HI gear necessary to sustain activity for protracted periods of time.

This doesn’t mean that we are burning the most fats when our heart rate is lowest—it just means that the greatest percentage of our energy comes from fats. By increasing our heart rate from its lowest point, we increase the amount of fats burned until the requirements of the task (as reflected by the heart rate) are high enough that a threshold is crossed—and the body is forced to switch to sugar in order to produce the necessary power.

(My favorite way of estimating at which point your body is most likely to switch from HI gear to LO gear is Phil Maffetone’s 180-Formula.)

Consequently, the problem with the power meter is that it doesn’t tell you whether the body is getting this energy from LO or from HI. The issue is simple—and it’s the very same one you would have if you’ve ever tried to go on a long roadtrip with a car that doesn’t shift up above second gear: you’re going to run out of fuel, blow the engine, or both.

During a marathon, just like during a road trip, your success depends on how well you’ve developed HI gear. Nobody argues that power (from LO gear) is incredibly important in a marathon—I often quote Owen Anderson, author of Running Science, who (in my opinion) famously said that “the marathon is a power race.” But the ability for you to get to the finish line (which is a precursor to racing to the finish line) is predicated on how well you developed HI gear.

“Hitting the wall” is a ubiquitous experience in the running community. I myself have hit the wall a dozen times. It’s almost a rite of passage—the badge of a “true” endurance athlete. It also means that muscle glycogen (a.k.a sugar) was depleted too soon: the runner was utilizing LO gear too much, and ate through all its fuel.

(HI gear—“fat-burning,” loosely speaking—draws from a massive fuel source. A 150 lb marathoner with 12% body fat has some 45,000 calories in the tank. LO gear has perhaps 2,000.)

Supposing that 60% of entrants at any given marathon are hitting the wall—although it wouldn’t surprise me if the real percentage was far higher—there is an epidemic of runners who despite their best intentions and best efforts, either (1) have not developed HI gear well enough, or (2) do not understand how to pace themselves in order to use just enough LO gear to go fast but not enough that they bonk at the halfway mark.

How do we factor this into training?

Let’s use the most classic bit of marathon training as an example: the long run. Since the marathon is a HI gear, fat-burning race, then we have to make sure that our long run is being fueled primarily by HI gear.

Suppose that some runner X has enough glycogen stores to fuel LO gear for 14 miles. If she’s been using LO gear to fuel the majority of her efforts up to the 14 mile mark, then she hasn’t really used HI gear to run even 1 mile.

This marathoner doesn’t really have a robust, well-developed HI gear to switch to. For her, a 14 mile run and a 16 mile run are extremely different experiences. The 14 mile run can be performed well with a powerful LO gear, but as soon as she bumps the distance up to 16 miles or more, her speed will drop dramatically—particularly towards the later miles.

(Marathon pace for the elite runner is only a few seconds per mile slower than half-marathon pace. In contrast, marathon pace for the recreational runner may be a third slower than half-marathon pace).

The problem isn’t that she hasn’t trained the mileage itself, but rather that the energy system that is supposed to handle high volumes of mileage was never really developed—so when she bumps up to a mileage that requires that fat-burning energy system, she grossly underperforms relative to her expectations.

Considering how many marathoners hit the wall, I believe that most of us don’t train HI gear on most of our long runs. This doesn’t mean we shouldn’t train LO gear or run long and fast in preparation for a marathon. It means that we need a reason for doing so—and we need to know when we’re crossing the threshold. Power meters aren’t enough. We need heart rate monitors: we need a window into what’s happening inside our body in real time.

Tales of Forgotten Subsystems, Part IV: The Sweating Mechanism.

The sweating mechanism is truly one of the most forgotten parts of the human body. Its influence in our athletic performance is so great that it’s really a mystery to me why more emphasis isn’t placed on training and developing it.

In a big way, our sweating mechanism is one of the things that sets us humans apart from the rest of the animal world. (The second sweatiest animal, the horse, only has about one-fifth of the sweat glands, per unit of skin, that we do). There must be a good reason we have a five-hundred percent sweating advantage over the next-best sweater in the animal world.

And yet, not only do we gloss over this massive mechanism to focus on sexier components of athletic training, but we actively shun it in society. We deride people who sweat a lot, and turn the very act of sweating into a social faux-pas.

Discussing that irony is an essay in itself.

Sweating is one of the things that makes us human. It is intricately tied to a multitude of other traits that identify us among animals: why we have little to no hair covering our bodies, why we have big brains, and even why we stand erect.

In Waterlogged, Timothy Noakes explains how these traits all come together in the human animal. As desert endurance hunters, it was necessary for humans to have big brains, in order to think abstractly and plan pursuits that would last for many hours into the future. But big brains aren’t enough. The air that’s closest to the ground (where most four-legged animals live) is also the hottest. In that hot air, the human brain—our supercomputer, the reason we outclass every other animal on the plains and otherwise—will overheat, and force the body to halt all athletic activity.

So how did we get around this problem?

In two ways: First, by standing up. This not only takes our center mass outside of the hottest part of the terrain, but it also puts our body in a vertical position, meaning that, during the hottest part of the day, we have much less surface area exposed to direct sunlight (than say a deer). Second, by dramatically increasing the amount of sweat glands, we can take advantage of the wind. Because our skin is uncovered, sweat lets the wind take heat directly from our skin, resulting in massive convective heat loss that other animals just can’t match.

From "Waterlogged: The Serious Problem of Overhydration in Endurance Sports" (Noakes, 2012).
From “Waterlogged: The Serious Problem of Overhydration in Endurance Sports” (Noakes, 2012).

(When an animal’s skin is covered by fur, the majority of their body heat remains trapped in that fur layer, and never gets exposed to the wind). In other words, while most animals were “designed,” if you will, for heat retention, we humans were “designed” for heat loss. Talk about natural athletes.

Thanks to this confluence of extraordinary adaptations, we can bring the rest of the features of the human body—our pack dynamics, our nimble physique, our massive aerobic engine, and the supercomputer that allows for productive, recursive symbolic manipulation (the human brain)—to bear on the hunt.

Given all of this, it’s amazing that we think of ourselves as frail, sedentary creatures. We are the athletes of the animal world, being able to run down just about every ungulate but camelids (llamas, camels, etc.) because we can’t drink saltwater (while most desert ungulates can), because we choose slow (and relatively inefficient) two-legged propulsion over quick and efficient four-legged propulsion, and because we play hardball with the desert climate—betting our internal water on the idea that we’ll be able to chase down that deer and still be able to replenish the water we lost. We take all of these apparent disadvantages and use them to our advantage.

And we can run down these “athletic” animals because our brains use 20% of our oxygen and 16% of our energy. (Comparatively, the brains of other mammals use between 2 and 10% of their total energy).

The powerful sweating mechanism lets humans act like that annoying poker player a lot of us know—while everyone else at the table is betting in a friendly, conservative manner, they’re changing the rules, out to make money, constantly going all-in.

Our sweating mechanism lets us fundamentally change the game. While other animals are stuck playing conservatively, trying to lower their body heat in a body designed for scarcity—a body that is all about water retention and heat retention (to save energy in the long run)we humans exploit this conservative game: we force animals to play by our rules.

It’s just like that poker game: because other animals can’t spend water fast enough, we humans play our aggressive game, betting that they’ll run out of chips before we do.

Next time we run in the heat, let’s remember this. When it’s so hot that running becomes uncomfortable, let’s remember that by unlocking our sweating capacity—by training the sweating mechanism just like we’d train any other muscle—we’re developing a crucial component of our athletic potential. Also, we’re getting in touch with one of the very things that makes us human.

Can everyone run?

A few weeks ago I was pulled into a conversation about running in La Paz, Mexico. I was asked incredulously by a good friend whether running was for everyone. In honor of the Baja 1000 off-road race, which recently concluded in La Paz, I answered with this:

“In order to run properly, a lot of us have to shake off the rust, change a few parts, and do some major tune-ups. And even though a few people out there are trophy trucks, every last one of us is at least a Jeep.”

Only one person can win the Boston Marathon every year, but (barring severe injuries and deformities), every one of us can aspire to run a marathon with the certainty that we will finish the race as healthy as we started it.

Shout out to the Vildosola family and racing team: good friends and constant winners of the Baja 1000.