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Nutrition: Fueling Your Brain For Running

Perform better by taking stuff that makes running feel easier.

Perform better by taking stuff that makes running feel easier.

If you run at any given pace long enough, you will eventually get tired and slow down. Start running at 50 percent of your maximum sprint speed and you might last a few hours, assuming you’re fit. Start running at 75 percent of your maximum sprint speed and you’ll only last a few minutes.

Various changes occur in your body as you run toward fatigue. The specific changes depend on your speed. Some of these changes can be used to predict the point at which you’ll become exhausted. Blood lactate level, muscle glycogen level, breathing rate and core body temperature are among the variables that scientists can use to anticipate the onset of fatigue in different circumstances. But there’s one variable that predicts fatigue at all exercise intensities better than any other: perceived exertion, or how difficult the exercise effort feels.

Perceived exertion increases linearly throughout sustained exercise at any given intensity. Thus, scientists can use the rate of increase of a runner’s perception of exertion to accurately predict how much longer he or she will last.

RELATED: How To Fuel For A Morning Run

Why is the intangible psychological variable of perceived exertion a better predictor of exercise fatigue than any physiological variable? Some scientists believe it’s because the feeling of fatigue is the real cause of fatigue. In other words, we always slow down when we feel exhausted because we feel exhausted.

Strong evidence in support of this idea comes from studies demonstrating that particular nutrients or drugs enhance exercise performance by acting on the brain in ways that reduce perceived effort. But in addition to proving that the feeling of fatigue is the cause of fatigue in exercise, these studies also reveal ways that everyday runners like you and me can enhance our race performance.

On the following pages are four nutrients and legal drugs that are proven to boost endurance capacity by making running feel easier.


Carbohydrate enhances running performance by increasing the availability of “premium” glucose fuel in the working muscles. Right? Maybe not.

A series of studies performed by a team of scientists at the University of Birmingham, England, has shown that endurance performance is increased when athletes merely swish a sports drink around in their mouths and spit it out periodically during exercise. The reason is that the carbs activate carbohydrate receptors in the brain that communicate with a part of the brain that regulates perceived exertion. The result is a decrease in perceived exertion that boosts performance.

It’s unlikely that a carbohydrate mouth rinse can fully match all of the benefits of actually swallowing a sports drink. For example, swallowing a sports drink rehydrates as well as supplies energy. But in running, where it is difficult to drink a lot, swishing and spitting a sports drink may be a good complement to ingesting it.

RELATED: The 10 Best Carbohydrate Sources For Runners


Fifteen years ago, before the role of the brain in exercise performance was much appreciated, scientists believed that caffeine enhanced endurance exercise performance by increasing fat burning. It is now known that caffeine enhances endurance performance by blocking adenosine receptors in the brain and thereby reducing perceived exertion.

By reducing the perception of effort associated with exercise at any given intensity, caffeine increases the intensity of exercise that is associated with the maximum tolerable degree of perceived exertion.

RELATED: Is Caffeine Truly Dehydrating?


Menthol is an organic compound obtained from mint oils that is known for its cooling taste and feel. Menthol does not actually cool the tongue or the skin when it makes contact with either; it just tricks the brain into perceiving a cooling effect.

Can you see where this one is headed? That’s right: In a 2009 study, researchers found that rinsing the mouth out with a menthol solution every 10 minutes increased cycling endurance in the heat by 9 percent compared to a placebo. In this case, the cyclists were asked to ride at a fixed intensity until they were exhausted. Perceived exertion measurements revealed that menthol made this fixed intensity feel easier to the subjects, and that’s why they sustained it longer.

RELATED: Menthol Improves Exercise Performance In The Heat


A series of studies led by Michael Saunders at James Madison University has shown that sports drinks containing a small amount of protein, which is not a traditional sports drink ingredient, along with the usual amount of carbohydrate are more effective than conventional sports drinks containing carbs and no protein. It is still not clear why this is so, but in a 2006 presentation at the Annual Meeting of the American College of Sports Medicine, Saunders revealed that the beneficial effect of protein on endurance performance is at least partly due to a reduction in perceived exertion.

One possibility is that ingesting protein with carbs during exercise increases amino acid levels in the blood. There is some evidence that elevated blood amino acids delay brain-based exercise fatigue. Another possibility is that ingesting protein during exercise reduces perceived exertion by reducing muscle damage. Carb-protein sports drinks are, in fact, proven to reduce muscle damage during exercise compared to carb-only sports drinks.

RELATED: The 10 Best Protein Sources For Runners


About The Author:

Matt Fitzgerald is the author of numerous books, including Racing Weight: How To Get Lean For Peak Performance (VeloPress, 2012). He is also a Training Intelligence Specialist for PEAR Sports. To learn more about Matt visit