The Runner’s Catch-22, Part 2: Power Facilitates Endurance.

In my first post of this series, I discussed a very common training problem plaguing the beginner runner: that it takes a certain amount of power to habitually produce an efficient running cadence (in the ballpark of 180 steps per minute, or spm), and it takes incrementally more power to produce it over longer and longer periods of time.

Enter the beginner, relatively untrained runner, who aspires to run longer races such as marathons. While it’s quite possible to run at 100% of maximum power output for 100 yards, it’s necessary to run longer distances at a decreasing percentage of the body’s total power output: in order to sustain activity for the long periods of time in which it takes to run a marathon, a runner must be working at around 55-65% of their maximum power output.

The problem is that producing an efficient cadence takes power. What happens if it takes 85 or 90% of your total power output to produce an efficient cadence? You won’t be able to sustain that cadence for a mile, let alone a marathon.

(This is a bigger problem than it seems.)

Think about deadlifting a 250 lb barbell. It’s not just about being able to lift the damn thing. At that weight, you should be able to (say) maintain the shape of the lower back, relax the shoulders, and produce a proper hip flexion and extension through the entire movement. The point is that it’s not just nice to be able to meet the minimum power and mobility requirements for the deadlift. You have to, or you’re flirting with injury.

Same thing for the marathon—it’s about being powerful enough to sustain a cadence in the ballpark of 180 spm for the duration of the entire race (for starters). This means that you need to be a good bit more powerful to run a marathon than to run a 5k.

In order to produce a certain cadence for a long period of time, you must be more powerful than to produce that same cadence over shorter periods.

 Over the course of this series, we’ll keep coming back to the same issue: in order to run well, the muscles need to be powerful enough to produce that cadence. If they’re not, they’re less efficient. Let me be completely clear: a powerful runner who can hit 180 spm habitually is more efficient than one who can’t. Let me reiterate this: if you are powerful, you get an added efficiency bonus that a less powerful runner doesn’t have. One last time: if you’re weak, you’re slow and inefficient, but if you’re powerful, you’re fast and efficient.

There is a crazy tangle of ironies to be exposed here: when the muscles are too weak to produce a cadence of 180, it takes a lot more muscle power to be able to run at the same speed. But because your muscles are weak, the speed you are able to run at is much, much slower than you’d expect if you supposed that both the fast and the slow runner were equally efficient.

If you’re powerful enough to produce a cadence of 180 for 50 or 60 miles (in other words, really powerful) you get massive dividends in energy savings.

(This is related to why the “correct” running form—not just for sprinting, but for all running speeds—is the one aligns the body in such a way to help it produce the most power.)

Thanks to this, runners like Jim Walmsley are able to sustain blazing speeds for very long periods of time. Gear Junkie reports that Walmsley recently crushed Rob Krar’s Grand Canyon rim-to-rim-to-rim record, running 42 miles with over 40 thousand feet of elevation gain (and another 40,000 of elevation loss) in just over 5 hours and 55 minutes.

Power is necessary for endurance for very specific reasons. In order to produce endurance—a.k.a. to stay in activity for long periods of time—you need to be burning fuel for long periods of time. But the body’s fuels (fat and sugar) aren’t created equal. The body burns less fats and more sugar as it works at a higher percentage of its total power output—a problem because even a very lean body stores about 100 times more calories in fats than it does in sugars.

Let’s say you’re trying to run at an efficient cadence. The less powerful you are, the more sugars you’ll have to be burning to sustain that cadence. Even if you’re burning 40% sugar to sustain an efficient cadence, you’ll run out of sugars that much more quickly than a more powerful athlete—who might only need to burn, say, 15% sugar to sustain the same cadence.

At some point, you’ll be left with 2 choices: (1) stop running, (2) reduce your cadence (and speed) to the point that you’re burning almost only fats.

Notice how stark these choices are: number one means that you just can’t run as far as the more powerful athlete. And number two means that now that you’ve bonked/hit The Wall—yes, this is what “hitting The Wall” means—you need to run the rest of the distance less efficiently than you’ve been doing so far. Got it? Now that you’re exhausted, you need to spend more energy per mile for the rest of the run.

We’re getting at what it really means to be “ready” to run a marathon—or any other race. It isn’t just about being capable of finishing itin the sense that your body didn’t fall apart before you got to the end. You need to be able to run the whole thing above a minimum threshold of performance. (Now you tell me what that is.)

7 thoughts on “The Runner’s Catch-22, Part 2: Power Facilitates Endurance.”

  1. I trained myself to run at 180 spm (using a metronome) but I’m still pretty slow. I can currently run 5k in about 24 minutes, and a half marathon in around 2 hours. I reckon I’m inefficient as well as lacking in power, so how come I run everywhere at 180spm?

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    1. The short answer is: because you shortened your stride length in order to maintain a high cadence. So, there’s 2 parts to the story of speed: (1) a high cadence AND being able to produce it at (2) your body’s comfortable stride length.

      My guess is that you became efficient by shortening your stride length INSTEAD of increasing power. (At 180 spm, your energy return almost certainly is high.)

      But the problem is that efficiency isn’t the ONLY condition necessary for becoming more powerful. Being able to produce 180 spm at ANY stride length is the minimum power requirement to successfully use the energy return systems that produce a “genuine” running movement. But in order to be fast, you need to produce 180 spm (and higher cadences) first with a longer stride length (sprinting) and then at a lower intensity (endurance running).

      So you need to become efficient first to be fast later, but being efficient does NOT mean that you’re fast.

      Maintaining (1) a fast stride rate with (2) a long stride at (3) a low intensity is what runners like Jim Walmsley are able to do. This is why I’m writing about power in relation to endurance. 180 spm is the bare minimum to be efficient, but to be “a powerful runner” you need to be able to produce 180 spm (and above) with an ever larger range of motion.

      If you want to be fast at aerobic distances, you’ll have to be able to produce 180 spm with a medium-large range of motion at an aerobic intensity (55-65% Vo2 Max).

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      1. So then… for people like me… who need to retrain their body to get used to a proper running stride length because we’ve been shuffling along for a few years… Is it simply a matter of incorporating shorter runs at the proper stride (which at first will be less efficient and higher HR)…? Or to put it another way… in order to break my shuffle…. do I keep shuffling a few times week for aerobic fitness and judiciously learn to run fast? Or do I stop all shuffling and run properly every fun – accepting my milage will drop but that I will earn that endurance back over time.

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