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If you want to level up in racing, you’ll need to level up your fueling. Some endurance athletes take the “wing it” or “this worked for me before” approach, when in reality, the fueling plan should be highly tested and adapted for specific goal races. You’ll want to adapt your fueling plan for weather, terrain, duration, intensity, and other competition factors. Here’s how to adjust your fueling plan to meet your competitive goals.
If you are in the infancy of figuring out your fueling plan, the first step to dialing it all in is to ensure that it contains all three components: fluids, electrolytes (particularly sodium), and calories. Once the basics have been identified, the plan should evolve and necessary adjustments should be made during every training cycle for target races based on distance, terrain, altitude, and climate.
The Basic Components to Your Fueling Plan
Take in enough calories—and don’t forget the carbs!
Think of the calories as the energy/gas to fuel your system. Your body has a limited amount of stored carbohydrate in its muscles and liver (only 1,800-2,000 calories worth!). Once these are emptied, the body relies on fat and protein (muscle breakdown) to fuel itself, which unfortunately, is a slower process, causing you to feel lower energy and increase your risk of a bonk. In order to avoid the dreaded bonk, it is recommended to take in at least 30 grams of carbohydrate/hour but this can be increased up to 90 grams per hour before the gastrointestinal system becomes more taxed. It is important to keep in mind that if you are taking in higher amounts of carbohydrate per hour, varying the sugar types (glucose and fructose) is recommended due to the limited number of individual transporters (1).
An average endurance athlete can easily expend 600-1,000 calories per hour during training and racing. A good target range is to replace around 30-40 percent of those, which breaks down to around 180-400 calories per hour. Keep in mind that calories can come from a variety of sources including: hydration mix, gels, chews, food blends, and whole foods. You must be strategic with logistics, palatability, and portability of calorie choices for yourself depending on your target race.
Hydrate, hydrate, hydrate—but don’t overdo it!
Fluid balance in the body is important to maintain plasma volume and exercise capacity, as well as avoiding heat illnesses. It has been demonstrated that losses of more than 2 percent in body weight can contribute to increased levels of fatigue and inhibit cognitive performance (2). On the other hand, we don’t want to over-hydrate and end up with hyponatremia. Therefore, determining an appropriate fluid intake amount for yourself during training and racing is key.
While there is no perfect way to determine fluid loss rates, you can get a good estimate at home by weighing yourself naked pre and post exercise and recording your losses during an easy training session. It is not recommended to record losses during higher intensity or longer training sessions (more than 90 minutes) due to potential glycogen losses skewing the results. Once you have your losses estimated, a good target for intake is about 75-100 percent replenishment every hour. (Example: 1 pound of loss in an hour would equal 16 ounces. Appropriate fluid replenishment rates would then be 12-16 ouces/hour). If you do not have access to a scale to perform fluid loss testing, a good starting place is 16-20 ounces of fluid consumption every hour.
Ensure you’ve got your electrolytes
Electrolytes like sodium, potassium, calcium, and magnesium all help maintain some level of fluid balance, muscle contraction, and nutrient utilization. Fueling plans typically focus on sodium intake due to it being the electrolyte that is lost in the highest amounts in sweat. When considering sodium replenishment rates, it can be a good idea to consider sodium sweat concentration testing at home from a company like Levelen and replacing about 75 percent of your sodium losses every hour. Otherwise, you can use the general recommended range of 250-500 mg/hour.
Once you have your three keys dialed in for your base fueling plan, adjustments need to be considered for race distance, terrain, and climate.
Increases or decreases in race distance require you to think about increasing or decreasing calorie consumption every hour. For longer races, bumping up your calorie intake every hour can be helpful and since the pace is slower, less blood is diverted away from the gut allowing for a higher amount of intake. Think about it this way, the longer you are out there, the bigger hole you are digging yourself into. Higher calorie intake per hour can help keep you going for those longer efforts.
As race distance increases, changes to the fueling types can be considered. Carbohydrates are still needed but adding in some protein and fat can be beneficial to help try and prevent palate fatigue as well as increase satiety levels. Keep in mind that protein and fat are still harder to digest so try not to overdo intake all at once.
If you are planning on racing on hilly or rocky terrain, one must consider the duration of time you will be out racing as these efforts will increase the time on course and the energy requirements overall (3). Hills require increased effort overall, and utilizing easy to digest fueling sources like gels during hilly sections of a training session or race can be helpful to prevent GI distress.
Increases in altitude can cause a decrease in appetite but an increase in overall carbohydrate requirements, as well as increased fluid and electrolyte requirements (3). It is important to ensure that logistics for how to carry and take in higher amounts of fluid, electrolytes, and calories are done ahead of time and anticipated, even if an athlete does not live at altitude. If possible, taking training trips to altitude to test your nutrition plan are recommended as this variable can be more difficult to navigate from a fueling standpoint.
Heat and humidity challenge our cooling capabilities due to decreased ability to transfer heat and ability to reduce evaporative heat exchange. This can cause an increased need for fluid and electrolyte consumption each hour. Measuring fluid loss rates in different climates can be helpful in determining fluid and corresponding electrolyte needs in climate variations. If living in a cooler climate, consider doing this in a gym setting to get a better sense of where you stand in the heat.
Hotter climates may also change palate preferences and may make sweeter options feel less appealing. Having savory choices like baby red potatoes with salt or tortilla roll-ups can help combat this issue. In colder climates, it is important to come up with fueling choices that don’t freeze and anticipate insulation strategies to prevent hydration from freezing.
You must be strategic with your base fueling plan, taking the time to put it together and practice it at least 2-3 months before your target event to allow for you to find what works for you and allow for gut adaptations to occur. Once you’ve got your base plan, it’s important to keep in mind the adjustments you may need to make for race day or your future race alternatives.
- Jeukendrup AE. Carbohydrate and exercise performance: the role of multiple transportable carbohydrates. Curr Opin Clin Nutr Metab Care. 2010 Jul;13(4):452-7. doi: 10.1097/MCO.0b013e328339de9f. PMID: 20574242.
- Cheuvront SN, Kenefick RW. Dehydration: physiology, assessment, and performance effects. Compr Physiol. 2014 Jan;4(1):257-85. doi: 10.1002/cphy.c130017. PMID: 24692140.
- Tiller, N.B., Roberts, J.D., Beasley, L. et al. International Society of Sports Nutrition Position Stand: nutritional considerations for single-stage ultra-marathon training and racing. J Int Soc Sports Nutr 16, 50 (2019). https://doi.org/10.1186/s12970-019-0312-9