Carbohydrate Considerations For Endurance Athletes/Enthusiasts

When it comes to nutrition, there are general principles that apply to everyone regardless of their goals. However, for those engaged in specific types of athletic endeavors, it may be beneficial to incorporate some sport specific considerations to optimize training and maximize performance during competition or other events.

Endurance athletes (distance runners, triathletes, distance swimmers, etc.) have a number of unique requirements above and beyond simply eating enough food and staying hydrated. This post touches on some key concepts for consideration specifically related to carbohydrate intake.

Let me preface this by saying there are numerous approaches to take when it comes to performance nutrition and it is highly individual. So, with that said, don’t feel like this is the only approach or that if you come across differences of opinion that one of us is “wrong.” There are very few black & white areas when it comes to any nutrition-related topic. However, the information I’m sharing here has strong research support.

Are Carbohydrates Important?

Of the 3 macronutrients (protein, fat, and carbohydrate), carbohydrates are the only non-essential nutrient. Our bodies can become adapted to function quite well without carbohydrate which is a state we would refer to as “fat adapted.” While carbohydrates are not essential, they are typically quite useful when it comes to performance-related activities due to the fact that it is much quicker to utilize them for energy.

Participants in high intensity sports and activities, almost without exception, will benefit from some supply of carbohydrate in the form of muscle glycogen. This is the stored form of carbohydrate. Endurance athletes, on the other hand, may not require the same level of carbohydrate availability.

A metabolically healthy body has the ability to switch between fuel sources as needed. During lower intensity, longer duration periods, it can utilize fat as its primary source while easily switching to glycogen during times of higher intensity or when it needs quick energy turnover. That said, for optimal performance, nothing beats an adequate supply of carbohydrate availability for those engaged in longer durations of even light to moderate levels of intensity.

Daily Carbohydrate Intake

The ideal amount of daily carbohydrate intake depends on your individual training goals and energy needs. A simple phrase to remember is “fuel for the work required.” We’ll talk about that a bit more in a moment. That said, here are some general guidelines from a 2011 paper from Burke et al pointing out a general recommended range of carbohydrate intake in grams per kg or pound of body weight (e.g. if you are shooting for 2.2g/lb and weigh 180 lbs, you would aim for 3.2 x 170 = 544g):

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These numbers may seem high when you run the calculations for yourself. However, keep in mind that these are NOT for optimizing fat loss goals, but rather, optimizing performance. Also, keep in mind that if you have a higher fat intake, you would want to adjust these numbers to according to additional fat intake (decrease carbs) if you are trying to maintain body weight throughout the training cycle. Ultimately weight is determined by your overall calorie intake, so keep that in mind if your dietary preferences lean higher in fat.

BEFORE Event/Training

It used to be thought that for long duration training/events, you should first deplete glycogen by eating a low-carb intake followed by what’s called “supercompensation” where you would then load with high amounts of carbohydrate. Sherman et al reported in a 1981 paper that “carbohydrate loading is of no benefit to performance for trained runners during a 20.9-km run.” So, you can use one of two options for loading carbohydrate prior to your event. The method you choose is individual and should be based on your personal experience. If you have an event coming up, you may want to consider a trial run sometime prior to the event as it’s not a good idea to experiment the big day:

  • Option 1: Use a very high carbohydrate intake 24 hours prior to your training/event with an intake in the range of ~12g/kg (5.5g/lb) of body weight.
  • Option 2: Rather than forcing extremely high amounts of carbohydrate in a single day, a more practical approach (and just as effective) for many is to load over a 3-4 day period leading up to the event. In this case, you would aim for 7-12g/kg (3.2-5.5g/lb) of body weight, again depending on the individual.

Day of Training/Event

On the day of your long training session or event, it is recommended to take in 1-4g/kg (0.5-1.8g/lb) of carbohydrate 1-4 hours prior to your session. This should primarily consist of easily digestible carbohydrates (low in fat and low in fiber) as you get closer to the start of the training/event. This will help minimize gut distress which you definitely do not want during a long outing.

DURING Event/Training

The amount of carbohydrate you consume during the training/event will depend on several factors: how much you consumed in the day(s) leading up to the event/training, the level of intensity, and the duration of the activity. A higher level of intensity will require greater carbohydrate utilization during the session and likewise, a longer duration also requires a greater amount of carbohydrate.

For durations of less than 70 minutes, if you have adequately prepared ahead of time, you will not likely need any additional carbohydrate to maintain peak performance.

For durations exceeding 70 minutes, you may benefit from the following general guidelines:

  • If you are consuming a single carbohydrate source such as glucose only, your body has the ability to utilize ~60g/h.
  • If you are consuming a source of multiple transportable carbohydrates such as a blend of glucose and fructose, because of the different transport mechanisms your body can utilize ~90g/h.
  • NOTE: High carbohydrate intakes during exercise require GI training/adaptation to improve tolerance. This is where you may want to do some self-testing during your normal training cycles.

AFTER Event/Training (Recovery)

There are several factors when it comes to recovery after a long endurance bout. Muscle protein synthesis, or the building/repairing of muscle requires adequate complete protein, however, it does not require carbohydrate. In general, make sure to take in 0.4g/kg (0.2g/lb) body weight of protein after your training session or just use a round number of 30-40g as that will generally take care of the needs of most people.

For replenishment of the glycogen used during the event/training, this may or may not be a concern. The key factors in determining the importance of this are:

  • Duration of the recovery period (when will you next train).
  • When is the next glycogen depleting session

If glycogen replenishment is needed, a good general rule of thumb is to aim for 1-2g/kg (0.5-1g/lb) per hour for the first 4 hours returning to normal intakes after. In general, you want to aim for high GI carbohydrates that have fast digestion and absorption and thus increase blood glucose quickly. Of note, caffeine has been shown to help with this process as well.

Finally, there is the important question of whether you even want to replenish glycogen as there are potential benefits to training, recovering, and sleeping on low carbohydrate availability. We won’t go into that now as that is a topic for an entire article but just know that this is an exciting area of research and implementation in the area of performance nutrition.

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