Sprint

With wide shots, steep angles, and far zoom, TV cameras can make some of the fastest people in the world seem like they're going for a brisk jog. But the numbers tell a different story.

Usain Bolt -- an exceptional sprinter by any measure -- runs 100m at an average pace of around 22mph, and once hit a top speed of around 27mph. That's around double the speed limit of a typical school zone. On the other hand, elite marathoner Eliud Kipchoge ran a mile in 4m37s, for an average speed of 13mph. Most treadmills top out at or around that speed.

I'm standing at the bottom of a hill, probably around 5% grade. It's the longest, steepest, least-congested piece of sidewalk near me, mostly because it leads to nowhere. Its sole purpose, as far as I can tell, is to funnel people safely down from the hill and into the Staples Center, but people seem to prefer it as overflow parking. So most of the time, no one's there.

Push off from the glutes. Maximum contact time with the foot. Breathe (does it even matter if I breathe?)

I'm wincing, gnashing teeth, audibly groaning. When I finally get to the top, I look back. Doesn't seem that far.

But I feel different. I feel tired. But most surprisingly, I feel younger.

George Brooks was a young collegiate athlete interested in getting faster in the 400 yard dash. He asked his coach what the problem was, and his coach told him: "You have too much lactic acid and oxygen debt. Go read about it." So he did.

George Brooks wondered, Why is lactate high when there's an energy demand?

I've always hated running. And runners. From my aloof vantage point of serene, sedentary observation, I saw running, conceptually, as the kind of slow grind that could only be fueled by self-loathing. Who else, I wondered, would spoil a perfectly good day for no discernable, rational reason, by taking off in the middle of it and going for a run? Or worse, nullify every step by doing it on a treadmill?

It stretched the limits of my imagination that someone could put in so much all to go zero miles an hour. Yet they do.

I'm not talking about people who run to work, or run to catch a train. I also do those things, because they're practical, and I'm a Practical Man.

I suppose I don't judge these people so much as envy them. Like everyone else, I know exercise is good. I've felt the state-sanctioned high of endogenous morphines, a.k.a. endorphins, and the pleasant ache in my legs just before bed. It's just that pretty much every time running comes up, I can think of something else I'd rather be doing, unless there's a very good reason to do it.

One of those reasons, for me, is Ultimate Frisbee. First of all, I know Ultimate Frisbee isn't exactly a panty-dropper of a sport, but because it's essential to the point I'm about to make, I'll have to bear some shame.

I know implicitly somehow that Ultimate Frisbee involves a lot of running. But when I imagine playing Ultimate, the way it actually appears in my mind's eye, running doesn't come up. I forget I have legs at all. Time slows down. Picturing it, I'm like a camera gliding from position to position, until the point comes that the frisbee floats in the direction of my mental screen. Then, we really enter slow-mo. The Frisbee gets perceptually bigger. Then someone from the opposing team enters my field of view, also in slow-mo, also leaping into the same column of air that I now find myself in.

And we're both running at absolute, all-out, guts-to-the-spine top speed.

My teammates have always hated this about me by the way. Apparently -- and I think the stats back this up -- I suck at Ultimate Frisbee, because I sprint for everything. If you've ever thrown two tennis balls to a labrador at the same time, that's what it's like to watch me play. For those few seconds the Frisbee floats above all of us, I truly believe that if I just believe hard enough, I can make it anywhere on the field. Then I fail catastrophically, lose who I was supposed to cover, and promise my teammates I won't do it again.

But when the Frisbee floats right back into the air, I get amnesia.

If you're not familiar with the rules of Ultimate, one thing you must know is that you can't throw the Frisbee while moving. So all passes happen with a single leg planted on the ground. And when it comes to passing, I'm strangely calculating about it, to the extent that I'll sometimes run out the 10-second count because I'm thinking too hard. It's a totally pointless loss, since it results in an automatic turnover, and ditching the Frisbee is always a better option.

This all makes me wonder. Do I actually like Ultimate Frisbee, the rules and strategy of which I never really took the time to understand?

Or was it always the running?

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• Lactate is produced both aerobically and anaerobically. It's a myth that it's only produced by anaerobic processes
• Lactate accumulation doesn't cause fatigue
• There's some controversy about whether H⁺ causes fatigue, but it's probably not a major contributor
• ATP production isn't really an issue for muscles. It's not like you run dry with ATP. In theory you can use the circulating lactate as ATP
• So what causes muscular fatigue? Your mitochondria are awash in lactate, which they can burn for energy. Mitochondria can use that lactate to make ATP.
• "When you make so much lactate, your body adapts by making more mitochondria"

There are some new findings in exercise science that are hard to believe but nevertheless true.

One is that your body burns the same number of calories whether you exercise or not.^[1] When you take the stairs instead of the elevator, you do burn a little more in that moment, but your body compensates by burning fewer calories later on. The implication is that the only way to lose weight, or gain it, is to change how much you eat.

It also turns out that all people, including obese people, have pretty much the same metabolism, and that it doesn't really change from the time you're 20 until you're 60.^[1]

This gives you a whole new way to picture obesity. It's purely a problem of appetite. A healthy appetite has you eat just enough to maintain your weight. But if your appetite thinks you need to eat more than you really do, you'll steadily gain weight over time. An obese person is just as much to blame for their obesity as a driver is for overfilling the gas tank because the fuel gauge is broken.

So obesity starts in the brain. And this explains why the best solutions, like ozempic and gastic bypass, suppress your appetite. They fix the broken fuel gauge.

Another finding is that a few short, all-out sprints, can do as much for your cardiovascular health as an hour-lung run. Also, while you won't burn more calories from sprinting, you will, surprisingly, lose weight. This should all surprise you. If it doesn't, you should read on. And if it does, you should also read on.

Elite endurance athletes obsessed with their VO₂max. It's all they talk about. "VO₂max" is the maximum V(olume) of O(xygen)₂ you can deliver to your muscles, per second, per kg of bodyweight. Make that number higher and, all other things being equal, performance goes up.^[3]

A superhuman VO₂max is how marathoner Eliud Kipchoge is able to run just over 13 miles an hour for two straight hours. When Pheidippides did that in 490BC, he died. I'm not saying you'd die, but I'm also not saying you wouldn't. Not even Eliud's pacers, the people paid to keep up with him, can keep up with him. To a normal person, the rate that he can deliver oxygen to his muscles just seems so impossible.

Yet he's doing it the same way as any of us are: by converting oxygen and glucose to units of energy called ATP.

On top of all this fitness stuff, people with high VO₂ maxes tend to live marginally longer, and substantially healthier lives. They have denser bones, bigger hearts, and sweaty, muscly torsos. At least that's how I imagine them.

So in short, everyone should want to meet their soulmate, find their purpose, and have a higher VO₂ max. But how? We know that distance runners and velo cyclists have massive VO₂ maxes, but we don't all have time to run 100 miles a week or bike around in a circle all day. Perhaps there's a better way?

This is where the surprise comes in. In 1996[3], a study in athletes (since replicated) showed that that while moderate-intensity training improved endurance but not strength, short bouts of all-out effort (SIT training) improved strength but also endurance. They measured this by testing the athletes' VO₂ maxes before and after 6 weeks. The even bigger surprise was that while the VO₂ max went up in both groups, it went up even more in the SIT group.

Remember that the O₂ in VO₂ max stands for Oxygen. But the SIT athletes trained in the anaerobic zone, meaning their energy came from their energy stores, and not from O₂. In other words, the SIT group trained their oxygen delivery system, despite not really depending on it.

If all of this seems unlikely, it's because there's now there's a missing piece linking aerobic to anaerobic fitness. This leads us to another Big New Idea in exercise science.

When you generate energy anaerobically, you turn glucose into pyruvic acid and ATP (energy), and then turn the pyruvic acid into lactic acid. Lactic acid is the key difference here. If you were doing low-intensity aerobic exercise, you'd generate ATP from a different pathway without pyruvic acid and, crucially, make lactic adic much more slowly.

For centuries people thought that lactic acid made you weak. It was christened a waste product of an inefficient system. In the 1900s, when our main forms of transportation had a reputation for crapping in the streets, this might have seemed like a reasonable assumption.

Like most reasonable assumptions, it's wrong. Lactic acid is merely guilty by association. Yes, you make truckloads of it when you're working out hard, but it doesn't make your muscles weak. What lactic acid mainly does is gets shuttled from muscle to muscle and even to your heart and brain to be used as fuel. Which is super interesting and surprising, at least to me.

Turns out lactic acid is actually one of the good acids, like acid.

What brings all of this together was a very recent discovery that makes lactic acid seem like a downright hero: wherever it goes, it seems to stimulate angiogenesis -- literally "artery creation." This is one of the missing links between anaerobic exercise and endurance: more arteries means a higher VO₂ max. Since lactic acid also gets shuttled to the brain, it has the potential for angiogenesis there too. So SIT training has the potential not just to make you run fast, but also think fast.

Let's see what the numbers say about how SIT training affects the VO₂ max of a normal person. Consider these two workouts:

• 15 minutes: full-on sprint for 30 seconds, 6 times, with a 2 minute break in between
• 45 minutes: run at about 60% effort

Both of these will amp up your VO₂ max by up to 10% in a fairly short amount of time. Studies suggest that the more you do this, the faster you can get results, even as early as one week in. Note, however, that even 20s is a really long time to run top speed, and although this will crank up your lactic acid quite a bit, it's far from easy to do multiple times in a row.

Now, there's another way the lactic acid affects our bodies that goes beyond the cardiovascular system. Some of the lactic acid floating around floating around in your bloodstream gets combined with phenylalanine (an amino acid) to make lactoylphenylalanine, also called "Lac-Phe."

Until recently, no one knew what Lac-Phe was for. As far as anyone could tell, you made the Lac-Phe during a hard workout, and then the Lac-Phe went home to its Fam-Lee and called it a night. At least, that's what it seemed like, until we started looking at people who don't make any Lac-Phe. Those people can be spotted by their waistlines: they're overweight. Some scientists had a Big Idea: maybe that's not a total coincidence.^[2]

To test it, they injected both skinny and fat mice with Lac-Phe, and observed them for a while to see what happened to them. It was just like you gave them ozempic. The obese mice started eating half as much and losing weight -- but only the obese mice. The thin mice were totally unaffected by the Lac-Phe and kept doing whatever.

So to summarize the more intense the training, the more the lactic acid, the more the Lac-Phe, and the less you want to eat. Unless you're already thin. It's nice how it all just works out like that.

(If you're already running to your doctor to pick up some Lac-Phe well, it's not on the market yet. But I guess the point is, if you run there fast enough, you won't need it anyway.)

The Big Question I have to ask is: why does all of this fit together so darn well. Is it another "just-so" story, replacing yesterday's fad with today's? Or is there something innately human about intense exercise, that's not merely supplemental to a good life, but the basis of one?

Still, to say nothing about the connection to my persistence-hunting ancestors, the VO₂ max, the angiogenesis, the brain gains, the staying thin forever, and the ability to chase down thieves who snatch purses from old ladies -- it all really does motivate me. It's nice when you come across a new habit that can deliver so much for so little.

Having said that, I'm still lazy. And there's a part of me that wouldn't mind just posting up on a warm rock like a turtle for the rest of my life, taking slow, deep breaths from my butt.

Some references and notes

^[1]

^[1]

^[2]

An exercise-inducible metabolite that suppresses feeding and obesity

[3] https://pubmed.ncbi.nlm.nih.gov/8897392/

[3] There are some other things like lactate thresholds that are important too, but less so than the VO₂max.

https://www.frontiersin.org/articles/10.3389/fphys.2021.702252/full

[3] To get more oxygen to your muscles, you might try doing an exercise that raises your maximum heart rate. Turns out, your max heart rate is stuck right where it is, and will only go down with age. This is just an unfortunate fact of life.

[4] Turtles don't really "breathe through their butts." They have sacs inside their cloaca that they can pull water into, and what little oxygen is in the water diffuses into the sac. So I don't think turtles would claim this ability. I do, however, know some yogis who would.

ang showed that, during prolonged exercise in humans (40 min at moderate intensity), the blood [La-] reached a maximum after about 10 minutes of exercise and then declined, sometimes to pre-exercise [La-], whether the exercise ceased or not https://sci-hub.ru/10.1113/jp279963

Under the most severe fatigue conditions, intracellular [ATP] rarely fall below 60–70% of resting values in the whole-muscle [12–14], with the most severely depleted muscle fibers reaching ~20% of resting [ATP], or ~1.6–1.8 mM [15]. Even in these severe conditions, the [ATP] has not reached the level necessary to observe impairments in contractile function [12, 13]. Thus, barring the unlikely event of a pronounced intracellular compartmentalization of ATP, there is little-to-no evidence that high-intensity exercise is limited by the rate at which ATP can be synthesized and supplied to the myofibrillar and ion transport ATPases. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6656370/