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  • Monique Vuong, MS, RD

LET'S TALK ABOUT THAT C-WORD. PART II: EXERCISE AND PERFORMANCE

Updated: Jun 28, 2020


Ever have that experience of putting in all the time and effort at the gym only to feel like your performance has stalled, and you just aren't making any progress? Well, it may surprise you to know it could have to do with your carbohydrate intake.

Here's why. Your body's preferred and primary source of energy come from carbohydrates, and this is especially true during exercise. Because carbs can be rapidly converted to glucose for energy, it is premium fuel. Your body stores these carbohydrates as glycogen in two areas: 1) liver and 2) muscle. Throughout the day, your body draws energy from those glycogen reserves (from the liver to maintain blood sugar and for general body function, from muscle to fuel muscles during exercise), as well as from fat, in different proportions.

The ratio of what you burn varies depending on the activity. For low intensity or endurance activities, you need a slow and steady source of fuel, so your body switches to burning more fat because it is energy dense. For high-intensity and weightlifting exercises, on the other hand, your body switches to burning more carbohydrates. The reason for this is due to your body's oxygen consumption. Fat metabolism requires ~4x as much oxygen compared to glucose metabolism. It is an aerobic (oxygen-requiring) source of energy, whereas carbohydrates can be both an aerobic and anaerobic source of energy. For high-intensity exercise and weightlifting, you are consuming less oxygen and therefore are relying on anaerobic sources of energy. Additionally, carbs are rapidly converted energy when you need it most to increase performance. Without carbs, you will often experience what is commonly described as "hitting a wall". You physiologically can't increase your performance without the proper energy stores. At the same time, carbohydrates (and protein) are needed for exercise recovery and muscle building.

There is much more information that goes along with pre and post-workout nutrition, so I will save that for another post.

Hope this helped shed some light on the topic for you!


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