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Intra-workout Feeding: Fueling during Activity

During your run, your goal is to maintain your predetermined pace for the entire race, and have enough energy at the end for a final push to the finish. To accomplish this in runs lasting less than 120 minutes, your body needs an effective pre-workout meal, as discussed last week. For those running longer than that, it is likely your body will run out of carbohydrate stores before you reach the end of your race. Prevention of an empty tank is overcome by small intra-workout feedings of carbohydrate. Similar to the pre-workout, these carbohydrates go to the blood stream and are used as energy in priority over your glycogen stores. This keeps your reserves for later in the run when you need them most. Simply stated, it extends the miles you can run at a given intensity.

For half-marathoners, most will not need to plan for an intra-workout feeding. The race is not long enough to completely deplete carb reserves, unless the intensity is above a moderate exertion. If you are pushing your body to a high level of intensity, you might need some carbohydrate. Since the race is shorter, 8-12 ounces of sports drink is plenty of sugar to keep your body running smoothly. In a 13.1 mile race, plan to take in carbohydrate if needed at mile 7-9. Since we are trying to prevent a decline in energy, it is best to take the carbohydrate in before your energy crashes.

For those readers running the full marathon, intra-workout feeding is inevitable, unless you are following the ketogenic diet (more on that in a couple weeks!). Our body’s reserves of carbohydrate are simply not large enough to fuel the body for 26.2 miles, even with the best carb-loading and pre-workout planning. Since you know you will need the carbohydrate, testing of source and timing starts during training. Everyone will run out of fuel at a different pace, based on preparation, pace and level of fitness, but generally the first feeding should occur between miles 8-10. At this point your reserves are fairly depleted, and need to be preserved as long as possible. Small servings of simple carbohydrate in the range of 20-30g of carbohydrate is best. Some common options meeting this criteria are:

  • 1 apple
  • 1 banana
  • 5-6 dried apricots
  • ¼ cup dried berries (cran, blue etc)
  • ¾ cup dry cereal
  • 1 serving pretzel thins
  • 8oz sports beverage
  • 1 sports gel
  • 1 packet of sports beans

I recommend a variety of sources to keep your palate interested during the run, but different protocols work for different people. The ultimate goal is to consume simple carbohydrates low in fiber that are convenient to carry, easy to swallow, and appealing to your taste buds. If you do not like what you are eating, your body will likely reject it, which will not help your performance. It is best to test out a couple options during your long-runs. Once you exceed 12 miles in training, you can begin to add a carb source and assess how your body feels.

After the first feeding, the timing will rely heavily on your intensity and calorie needs. A large male running at moderate intensity is going to need a significantly more carbohydrate compared to an individual of smaller size. Typically, the feed points will be:

  • Miles 8-10
  • Miles- 13-15
  • Miles 18-20
  • Mile 22-24

In addition to a source of carbs at these points, many will sip on diluted sports drink throughout the event. This can help keep some sodium and potassium in your body. On hot days when more sodium is lost through sweat, it is imperative to increase the sources of salt and potassium, as well as increase fluid intake. The amount needed will vary based on age, gender, intensity and genetics. If you are concerned about your hydration status, please contact a Dietitian, and stay tuned for the hydration article in a few weeks!

Overall, intra-workout feeding is fairly simple. Using foods like apricots and bananas add potassium to the diet, and cereals, pretzels and sports drink provide sodium to a body losing electrolytes. Plan your feedings ahead of your decline in performance by starting conservatively in training and listening to your body. For more details on your personal needs, contact a Sports Dietitian to help you plan for performance!

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