Evan Lerner has a quite interesting article on seedmagazine.com about physical performance and exhaustion. That painful lactic acid throb? It’s mostly in your head:

The finish line is in sight, but you’re not going to make it. Your lungs are burning and deeply in oxygen debt. The muscle fibers in your legs have converted most of the carbohydrate supply in your body into lactic acid. This was a fine plan for generating the extra energy needed to keep you moving in the absence of adequate oxygen, but it is now making your quads and hamstrings feel like they are on fire – which is more or less the case. In short, your fuel tank is empty and you’re running on fumes. You are not going anywhere, except possibly to the ground in a heap.

The above scenario sounds totally plausible but is almost totally wrong. Runners are often at their fastest at the end of a race, when they should be the most tired. And, according to a new study, we can push ourselves harder when we expect to get a boost of energy from sugar, but long before those carbohydrates are actually absorbed. The experiment is clear evidence that our physical limits are less in our muscles and more in our minds.

The idea that muscle fatigue involves more than a lack of chemical energy is in some ways self-evident. Athletes perform better after consuming a sugar-laden energy drink, though the amount of energy contained therein is tiny compared to the reserves in their muscles. And according to a paper published earlier this month in The Journal of Physiology, athletes don’t even have to swallow those sugary drinks to feel a boost. The study – led by Ed Chambers, Matt Bridge, and David Jones at the University of Birmingham – cuts to the core of why we get tired at all.

This reminds me of a clever experiment led by Baba Shiv, of Stanford. (I describe this experiment in How We Decide.) He supplied a group of people with Sobe Adrenaline Rush, an “energy” drink that was supposed to make them feel more alert and energetic. (The drink contained a potent brew of sugar and caffeine which, the bottle promised, would impart “superior functionality”). Some participants paid full price for the drinks, while others were offered a discount. The participants were then asked to solve a series of word puzzles. Shiv found that people who paid discounted prices consistently solved about thirty percent fewer puzzles than the people who paid full price for the drinks. The subjects were convinced that the stuff on sale was much less potent, even though all the drinks were identical.

Why did the cheaper energy drink prove less effective? According to Shiv, consumers typically suffer from a version of the placebo effect. Since we expect cheaper goods to be less effective, they generally are less effective, even if they are identical to more expensive products. This is why brand-name aspirin works better than generic aspirin, or why Coke tastes better than cheaper colas, even if most consumers can’t tell the difference in blind taste tests.

I imagine a similar effect may be at work with athletes and physical exhaustion. The athletes who are convinced they’re in better shape are the ones that are mentally prepared to sprint towards the finish line. It’s a little easier for them to fight through the pain and persist, just like subjects given the non-discounted energy drink. Meanwhile, competitors who feel outmatched, or are maybe recovering from a nagging injury, might find these last-minute heroics to be a bit more challenging. In other words, everybody feels the pain – the real question is what we do with it.