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Burn the right fuel: Glycemic index and pre-class nutrition


AP Photo/Larry Crowe

Your martial arts class is far from over, but the clock seems to have frozen like Lake Michigan in January.  Many martial artists have experienced the excrutiating slowness of the last few minutes of class, as their muscles have depleted the last of their glycogen stores and every body part has seemingly turned into lead.

While overall fitness plays a role in endurance, pre-class nutrition is often neglected.  Many of you  rush to your martial arts class straight form work, often fighting traffic, public transit, and weather to get to that class you have been daydreaming about all day.  In the rush, many of you may stop to refuel your car, but not your body.

Carbohydrates are a key fuel for the body during physical activity, but not all carbohydrates are created equal.  Some carbohydrates can cause your blood sugar level to spike for a short period of time, then drop to a level lower than even before you ate.  Fortunately, there are other carbohydrates that keep your blood sugar elevated over a longer time, without the initial spike.

The measure of a carbohydrate's propensity to spike and crash your blood sugar is called the glycemic index.  The glycemic index is a numerical ranking of a carbohydrate from 0 to 100.  The ranking is based on blood sugar measurements from 10 healthy people over a two hour period, who have eaten the same amount of the same kind of carbohydrate. 

The carbohydrates that cause the blood sugar to spike have a high glycemic index (70 or above) and those that are able to maintain a steady level over the 2 hour period are assigned a lower glycemic index (55 and under).

So, how should this apply to pre-class nutrition?  Part of the answer lies in the length of your class.  If your class is under an hour, you may be able to eat a high glycemic index carb and have it last throughout the class

It is always better to err on the side of caution, however, and choose low glycemic index carbohydrates.  Studies have shown that low glycemic carbohydrates consumed before exercise can burn more fat.

When should you eat and what should you eat? Low glycemic carbohydrates should be eaten 60 to 90 minutes before class.  If you do not have enough time, try eating a mixture of low and high glycemic index carbs 15 to 30 minutes before class. 

Low glycemic foods also tend to be complex carbohydrates: 

  • Multi- and whole-grain bread
  • oat bran
  • brown rice
  • most fruits and vegetables

"White foods", such as white bread, potatoes, rice cakes, white sugar,  bakery products made from white flour, and anything containing white sugar, glucose, or high fructose corn syrup have high glycemic indexes.  Here is a fairly comprehensive list of the glycemic indices of various foods. 

An often overlooked fact is that the glycemic index of foods can be lowered by consuming them with proteins and fats.  So, a piece of cheese with some white bread will actually lower the overall glycemic index of the bread.  However, since most low glycemic foods also have a lot of fiber, this nutritional advantage is lost when "cutting" a high glycemic food.

Keep it simple by planning ahead, and having some low glycemic foods handy before class.  You pack your gi and your equipment ahead of time - pack some non-perishable food at the same time.

Fuel yourself with the right kind of food so that you have enough energy to maintain your focus throughout the class.  You've waited all day for this class - don't let a lack of fuel keep you from enjoying it to the end.

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