How Often Should You Fuel During Long Runs?

The Role Of Glycogen In Marathon Racing

One of the most important determinants of marathon success is how efficiently your body can use fat as a fuel source as opposed to carbohydrates. The more readily you can burn fat while running at marathon pace, the longer your glycogen stores will last–providing crucial energy for that last 10K.

Your body has a limited supply of glycogen available to fuel your working muscles. Most research has shown that you can run about 2 hours at marathon intensity before you run out of glycogen. For all but the fastest runners in the world, this is going to leave you far short of your goal.

MORE: Race Fueling Made Simple

Unfortunately, while helpful in extending glycogen stores, simply eating on the run won’t entirely replace all the glycogen you burn. Midrace fueling is limited by how quickly your digestive system can deliver the glycogen to your bloodstream and, under the duress of marathon racing, the stomach is not very efficient.

Therefore, it is critical that you find ways to optimize the amount of fat you burn while running at marathon pace. One of the most obvious places to look for these improvements is in the long run.

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