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Say Goodbye To Carb Loading

    In 2019 the definitive study (Fuchs, Gonzales, Loon) on fueling for performance was published. The learnings are only now trickling down to team sports.

    It all starts with ATP, the batteries that fire in your muscles to make them work. Each time they fire its pretty much a micro explosion. The coolest part is that we can recharge them really fast. It’s one of the capabilities that gives humans so much more endurance than most other mammals.

    How does ATP recharge?

    It recharges by converting the food you consume to glucose and combines it with oxygen. Our body stores glucose, at the ready, in our muscles and blood. This is basically our gas tank. This is where historically carb loading was an important part of athletic performance; it was important to fill the gas tank up in the day or two before a major competition or training session.

    But there’s a problem; athletes performing at a high level can blow through their glucose stores in under an hour in some cases. So we supplement by taking in carbohydrates during competition to top up the fuel tank. Simple carbohydrates convert to the glucose we need to power our muscles really quickly.

    In lab trials of the past we assessed how much carbohydrate an athlete can consume and, in turn, recharge ATP. Initial trials concluded that we could convert between 30 grams per hour. What happened above that was gut distress leading to cramping, gas, and other bad effects.

    Later trials tried different types of carbohydrates and the results started to look different. The final, and current, conclusion is that glucose and fructose take two different routes in the ATP cycle. If we max out each pathway by consuming glucose and fructose we have concluded that well trained athletes can convert about 90 grams per hour of carbohydrate when consuming at a ratio of 1 gram of glucose to .8 grams of fructose. For all but the most elite endurance athletes a 1:1 ratio is close enough.

    So What Does Fueling For Athletic Performance Look Like Now?

    We now know that we can simply fuel for the effort rather than topping off the fuel tank. These recommendations are for high level athletes working out or competing for less than 3 hours continuously.

    Pre-Fueling: In the 60-90 minutes prior to a workout or competition athletes should consume 60-90 grams of carbohydrates in a 1:1 ratio of glucose to fructose. This may require adaption for some but after a week or so of doing it most will be adapted.

    In game/workout: Fuel for the effort. At the low end, less intensity and/or smaller athletes, should consume at least 30 grams per hour. At the high end, more intensity and/or larger athletes, the ceiling is around 90 grams per hour.

    Post game/workout: After hard workouts or competitions athletes should consume approximately 1 gram of carbohydrate per kilogram of body weight starting immediately and they should space that out to limit gut distress but be finished within 60-90 minutes.

    What about protein?

    For nearly all college sports there is no need to consume protein or fat immediately before, during, or after intense efforts as the body takes about 4 hours to process protein and this will only bog down internal systems unnecessarily. Significant protein, fat, and fiber should be limited to 2-3 hours before intense efforts and 1 hour after.

    Referenced Studies

    Fructose co‐ingestion to increase carbohydrate availability in athletes. 2019 – Fuchs, Gonzales, Loon

    Assessing exogenous carbohydrate intake needed to optimize human endurance performance across sex: insights from modeling runners pursuing a sub-2-h marathon. 2024 – Cole J. Lukasiewicz, Kayla J. Vandiver, Elizabeth D. Albert,Brett S. Kirby, and Robert A. Jacobs

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