Thursday, August 19, 2010

On glycogen.

One of my readers recently submitted the following:

"I read something about how your body can use stored energy on runs. That is uses glycogen first and then fat (or vice versa). Can you teach it how to use the reserve when you get tired?"

Oh, well well. Glad you asked, dear reader! I'd be all too happy to discuss glycogen. Gly-wha? GLYCOGEN. It comes from carbohydrates, which your body breaks down into glucose, fructose and galactose. All of which are called upon as a source of energy that allows your body to function outside of exercise. What's left over is then turned into glycogen and stored in your muscles for later use. Like, for example, when you exercise. (I also read that glycogen is stored in the uterus of a pregnant woman, and that it helps nourish the growing baby within. But that doesn't really have anything to do with exercise. I just learned something new and thought I'd share, so back to it...) To understand how your body uses glycogen, you have to understand the difference between your aerobic and anaerobic systems.

Your aerobic system uses oxygen to find energy that's hidden throughout your body in the form of carbohydrates first, then protein and fat. It's typically activated during endurance-based workouts in an effort to keep the body at a place where it can sustain physical activity for a longer period of time. On the other hand, the anaerobic system works almost without oxygen as it relies entirely on the glycogen stored in your muscles to facilitate quick bursts of movement like sprints or jumps. Consequently, the anaerobic system kicks in first.

So, yes—your body uses stored energy. Even when you're running. And it does so naturally, so you don't have to worry about teaching it how to tap any energy on reserve. Your body is built to find energy wherever it can. First from carbohydrates appropriately stored as glycogen, which is why many runners choose to "carbo-load" before going the distance. As glycogen depletes, you start to hit the wall—a good sign that your body is using fat for energy. It also turns to protein, but protein isn't the best source of energy and we need it for muscle growth and repair (among other things). Needless to say, carbs are still the best source of energy which is why distance runners often rely on specialized sports drinks, bars, gels, beans and whathaveyou to up their carb count mid-run.

Essentially speaking, make sure you eat carbohydrates before, sometimes during, but especially after you exercise. Choose healthy carbohydrates and learn to eat the right amount—excess carbohydrates are stored as fat. So watch your fat intake, too. (I know. It's a vicious, never-ending thing.) 

Question: How do you typically "carbo-load" before a big race? And do you have a favorite healthy carbohydrate? Me, I love oats.

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