Fueling for Endurance Sport Starts
with CarbohydratesBreanne Nalder, MS, RDN
Last week I overheard a couple of elite endurance athletes in the locker room at the gym talking about training and nutrition. Specifically they were lamenting the fact that they had gained some weight over the holidays and were now gearing up for their season and looking to lose some of that holiday weight. One of them indicated that she was going to eliminate all grains from her diet, because she had heard that cutting out starchy carbs, like bread, was a good way to lose weight. And yes, there are a lot of success stories out there of people losing weight by “cutting carbs”...but most of them are not elite endurance athletes. Indeed, while a low carb diet may lead to quick weight loss, it will be at the expense of optimal performance. And since most athletes value performance above all else, they should also value carbohydrates consumed in the right amounts at the right time.
The Importance of Carbohydrates to Athletic Performance
The provision of adequate carbohydrate is essential for athletes, particularly endurance athletes. The availability of carbohydrate during endurance exercise determines the intensity and duration of exercise that the athlete will be able to complete. Since carbohydrate storage in the body is limited, carbohydrate recommendations are designed to ensure adequate substrate for exercise and recovery. Also, our brains run only on glucose, so maintaining adequate carbohydrate levels is essential in keeping focus throughout training and competition (it’s always a goal to avoid “bonking” right?).
The Concept of “Carbohydrate Availability”
For years endurance athletes have been told they should consume a “high carbohydrate diet” which has most often been defined as a percentage of the athlete’s total energy intake (i.e, 65%-75% of energy intake should come from carbohydrates). This “one size fits all” recommendation is not only vague but it overlooks the natural variability in an athlete’s carbohydrate needs as function of the variability in training. Thus, a recently published consensus statement by the International Olympic Committee suggested that a more accurate way to describe carbohydrate recommendations for athletes is in terms of carbohydrate availability (Burke et al. 2011). Carbohydrate availability addresses whether the athlete’s total carbohydrate intake and the timing of that intake around exercise or training maintains an adequate supply of carbohydrate for the muscles and central nervous system (“high carbohydrate availability”) or whether carbohydrate intake is inadequate leading to muscle and liver glycogen depletion (“low carbohydrate availability”). In simple terms, then, carbohydrate availability describes how well carbohydrate intake matches carbohydrate needs on a daily basis as well as before, during and after training.
Optimizing Carbohydrate Availability on a Daily Basis
To ensure optimal carbohydrate availability on a daily basis, athletes should aim to match their carbohydrate intake to their training load. The table below highlights optimal carbohydrate daily needs for different training loads in both grams per kilogram body weight and grams per pound of body weight (Burke et al. 2011)
|Light (rest day or < 1 hr light training)||3-5 g/kg or ~ 1.4-2.3 g/lb|
|Moderate (~1 hr of moderate intensity training)||5-7 g/kg or ~ 2.3-3g/lb|
|High (1-3 hr of moderate-to-high intensity training)||6-10 g/kg/d or ~ 2-7-4.5g/lb|
|Extreme (4-6 hr of moderate-to-high intensity training)||8-12 g/kg/d or ~ 3.6-5.5g/lb|
|Carbohydrate loading for endurance events (1-2 days prior to event)||7-12 g/kg or ~3-5.5g/lb|
Maximizing CHO availability before, during, and after exercise
Just as you should never embark on a long road trip without a full tank of gas, an endurance athlete should never start a prolonged (> 1hr) and/or intense training bout without adequate liver and muscle glycogen stores. Eating a carbohydrate-rich meal before a training bout will help top off both liver and muscle glycogen stores. The general rule of thumb is to consume 1 gram of carbohydrate per kilogram of body weight 1 hour before exercise, 2 grams of carbohydrate per kilogram of body weight if you have 2 hours before exercise and so on. The meal should be moderate in protein and low in fat. Minimize the amount of fiber in this meal to prevent stomach discomfort during exercise. Even if you are not hungry, you should have something to eat before a long workout. Some examples of pre-exercise meals include:
- Cereal (hot or cold) with low-fat milk and fruit
- Toast with peanut butter, jam and/or honey and fruit
- Pancakes or French toast with syrup and fruit
- Turkey sandwich with pretzels or baked chips
- Spaghetti with tomato sauce
- Large baked potato with low-fat toppings
- Chicken or tofu with rice
- Granola or high carbohydrate sports bar with fruit
During prolonged (< 1 hour) moderate-to-high intensity exercise, the provision of carbohydrate can help maintain blood glucose levels and provide glucose to the exercising muscles thereby delaying glycogen depletion and muscular fatigue. It is recommended that for training bouts lasting between 1-2.5 hours, carbohydrate be consumed at a rate of 30-60 grams per hour anything longer than 2.5 hours and intakes up to 90 grams per hour are advised. Carbohydrate consumed during exercise should be familiar an easily digestible. Research suggests that the form of carbohydrate consumed during exercise is really a matter of personal preference. So choose the gel, bar, beverage, block, bean, etc. that works best for you. (Note: it is always best to experiment with different sports foods during training- Never use a new sport food for the first time in a race!).
The goal of carbohydrate consumption post-exercise is glycogen replenishment and recovery. Historically, athletes were cautioned about the “window of opportunity” for glycogen replenishment and were thus advised to consume carbohydrate as soon as possible and within two hours post exercise for maximum glycogen replenishment. However, recent research indicates that immediate carbohydrate replenishment is only crucial IF your next exercise bout is within 8 hours or less (i.e., stage racing or 2+ workouts in 1 day). If this is the case then athletes should aim to consume 1-1.2 grams of carbohydrate per kilogram per hour for 4 hours. If you have more than 8 hours until the next workout, a healthy balanced meal within the next 2 hours is sufficient. The carbohydrate:protein ratio should be 2:1 in short, low- to medium-intensity workouts or 3:1 in long, high-intensity workouts. Examples of post-exercise foods include:
- Chocolate milk (or any non- dairy recovery drink if you don’t tolerate milk)
- A high carbohydrate sports bar (e.g., Clif bar) and sports drink
- Smoothie with yogurt and fruit (coconut can be a yummy milk alternative)
Train low, Compete High?
"Train low" has become a catchphrase among endurance athletes, although thankfully not a particularly common practice. Training with low glycogen stores is purported to enhance fat oxidation (thereby “burning more fat”) as well as spare muscle glycogen. While the limited research suggests that training with low muscle glycogen may increase cellular markers associated with training “adaptations” and fat oxidation during sub- maximal exercise intensities, benefits to endurance performance have not been demonstrated. In fact, research suggests that training with chronically low glycogen stores compromises performance both in training and competition (Burke 2010).
As an athlete, you are always working to improve performance. Being adequately fueled will help you get the most out of each workout and reach your athletic potential. Both whole foods and sport nutrition products play a role in your diet, so it is crucial to plan your meals and snacks based on time, convenience, and your own likes and dislikes. Practice proper sport nutrition so when it comes time to compete, you’re a ready, confident, well-fueled machine!
Breanne Nalder, M.S., R.D.N.
Registered Dietitian Nutritionist
phone: (801) 550-0434