You Always Have More to Give.

But willing your way there isn't how you get it.

We tend to think of fatigue as a muscular issue. Your quads get tired, you can feel the burning sensation, and then they just don’t work anymore. So you slow down or aren’t able to lift the weight.

But this simple idea masks the complex process that actually occurs. Your legs don’t decide how hard you can push. They influence it, provide information for how good or bad things are, but it’s your brain that makes the ultimate decision. And it can be fooled…at least for a while.

In a recent study, researchers put this to the test. They had runners complete a series of time trials in three separate conditions, consuming: water only, a carb mouth rinse, and a dissolvable carb strip.

When the runners swished and spit out a carb drink they ran 2% faster. When they consumed the dissolvable carb strip, they ran 3%.

Carbs enhance performance. That’s not a new finding, right? In both cases little to no carbohydrates were actually ingested or processed. They were either spit out, or in the case of the strip, only a tiny fraction is digested.

The carb rinse/strip was designed to fool the brain. We all have sensors in our mouth that essentially signal more fuel is on the way. Our brain thinks relief is coming, so it loosens the reins up just a touch. The carb strip probably had lower contact time with the sensors than the rinse method, so runners got a slightly bigger boost.

In another study, researchers looked at what happened in the brain when cyclists swished and spit sugar. Their brains reward and motor regions lit up. It’s as if the brain was saying: increase motivation and prepare to go to work. Interestingly, a artificial sweetners did not activate these regions. Showing it’s the carbs itself, not the taste that matters.

While the exact mechanisms are argued with different theories of fatigue, they all point in the same direction. Our brain is running a kind of predictive cost benefit analysis. How hard is this? How much fuel do I have? How far do I have to go? When it senses carbs in the mouth, it updates the fuel available estimate.

It’s utilizing past experience and current information to help us to decide what to do. In a novel situation, where danger seems like a possibility, it keeps a tight leash, sounding the alarm well before you’re in actual danger. This is why novices often have trouble pushing that hard in workouts. There brain is more protective, as it doesn’t know what to expect or where it’s own limits lie.

We can shift it’s inner calculus by giving it a better blueprint and information. If you’ve been in similar situations before, it knows when to sound the alarm. But as these carb studies show, we can also influence that calculus by shifting our signals.

In this case, by showing that carbs are on the way, it reduces effort and makes it seem a little bit more manageable. This is also one reason caffeine works as well. It makes things seem a little bit easier, and you feel more energized and focused.

It’s also why certain mental strategies help us out. When we break down the race, thinking about the next mile instead of the full marathon, our brain shifts the math. It starts thinking “Do I have the juice to get to the next mile…” which eases it a tad more managable. Similarly, if you’re hyperfixated on how your quads feel or if your breathing is heavy, your brain takes that into account, and might tighten the reins. You get stick in a doom loop, and it starts to feel way harder than it should.

We treat performance like a hardware problem: Vo2max, lactate threshold, etc. And that hardware absolutely matters. But the software (your brain) is regulating the whole system. We need to think of it as an interplay. The physiological shifts the calculus by altering capacity, fatigue signals, etc. But we can also work on the software itself. By what we’re focused on, how we frame competition, process poor races, or even take in fuel or supplements.

On the latter, it explains why conventional wisdom (don’t take fuel at mile 24-25, because it’s not long enough to be processed before the race is done), might be wrong. Sure, the fuel may never be digested, but the signal that more is on the way at just the time when you are falling apart could be the difference maker. Instead of a gel late in the race, maybe we should take a carb strip.

We always have more to give. But it’s not as simple as willing our way to get more out of ourselves. We need to shift the calculus. Sometimes that means “fooling” your brain, other times redirecting it, or altering how it interprets the various signals that help it form its calculation.

-Steve