Carbohydrates are the body’s first choice for fuel when working at higher intensities. Fat can be used for fuel, but fat requires greater amounts of oxygen to be burned efficiently, and as such, is burned in higher proportions when exercising at a more leisurely pace. For faster paces, carbohydrates do the heavy lifting and runners looking for top performance must eat properly for success.
Carbohydrates are stored in the body as glycogen, a long chain of compact carbohydrate molecules. Glycogen is stored in the muscles, as well as in the liver. The body can store approximately 2000 calories of carbohydrates in the form of glycogen. Research has shown that this amount can be increased to about 2200 calories by doing a carbohydrate depletion run 3-5 days before a race, followed by several days of increased carbohydrate consumption leading up to the race.
Runners have a long history of loading carbs in the days leading up to an important race. The longer the race, the more important it is to start days in advance with carb loading. Shorter races, such as 5k or 10k races, don’t require much more than a small high carbohydrate snack prior to the race. These races are short enough that they will not consume the body’s carbohydrate reserves.
Longer races, especially marathons and ultramarathons, have a high likelihood of consuming the body’s carb resources and require both carb loading before the race, and carb consumption during the race for top performance. The famous “wall” that is hit by marathoners in the final 6 miles of the race is a direct result of the body running out of carbohydrate resources and relying on a greater percentage of fat for fuel.
Ultramarathon runners perform at low enough intensities that carbohydrate reserves can be pushed further than in marathons. These runners will eventually consume the body’s glycogen and must consume carbs throughout the race in order to continue burning fat for fuel. A strategy for continued consumption of carbs throughout the race is essential for success.
Many runners use running as a means of exercising for weight loss. Running is simple, requires very little equipment, and is accessible to everyone. Those looking to lose weight, especially those with no performance goals, can do with fewer carbs. When losing weight, a calorie deficit is the name of the game, and fewer calories, and carbs are going to be a requirement for successful weight loss.
For runners interested in running at higher performance levels, carbohydrates are essential. Speed workouts, such as tempo runs, hill repeats, or intervals, by definition will be at higher intensities that require plenty of carbohydrates to complete the workout. Long runs are another high intensity workout that are improved with higher carb intake.
If you are going out for a long run, or speed work, then make sure that you consume sufficient carbohydrates before your run, as these workouts are a performance-oriented workout. The goal is to run hard and maintain pace, so carbs will be essential to perform the workout at the required intensity level.
After a race, or hard workout, the body’s hormonal environment is primed for storing carbohydrates as glycogen. Insulin levels spike immediately following a hard workout, opening the door for storing carbohydrates in muscles and in the liver. A high carbohydrate liquid should be consumed within 20 to 30 minutes of a race, or hard workout for maximum recovery. Carbohydrate recovery drinks, or even low fat chocolate milk are great choices for glycogen recovery.
While whole grain, slowly digested carbs are recommended for general health, runners need carbohydrates that will be quickly digested and shuttled into the bloodstream. The fiber in whole grain carbs slows the digestion process, as does high fat content, so these should be avoided, especially in the 20-30 minute post-workout recovery window.