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Make your own endurance fuel at ~3x lower cost, with a wide possibility of flavors and customizations. That’s cash towards your next race or investment into training, nutrition, and gear!
Endurance fueling – practice makes perfect
Single and multi-stage endurance events result in sizeable losses to energy stores, water, and electrolytes. Your endurance fuel should offset these losses and mitigate fatigue from dehydration and lower availability of fuel to contracting muscles. Experimentation and practice of fluid and food intake in training is important to quantify your appropriate level of carbohydrate and salt intake for events.
The risk of developing gastrointestinal (GI) distress increases twofold for those not accustomed to fluid and food ingestion during exercise,[1] and >30% of athletes exhibit one or more GI symptoms during exhaustive endurance events. [2] It’s likely attributable to a combination of maldigestion and malabsorption of nutrients, changes in transit time of nutrients through the gut, and improper fluid and nutrient intake. Experimentation and continued practice can be the difference between an all-time best and a DNF/DOR. Use training time wisely to understand what works/doesn’t work for you. Consider that your gut may not behave the same at hour one versus hour eight or more.
A good liquid endurance fuel will:
- Replace water. As little as 2% decrease in body water can impair performance [3], and insufficient fluid replacement may increase the frequency of GI symptoms.[4] Replacement rate can vary considerably based on climate, exertion, body composition, and other factors, but a good base is in the 0.45-0.75 L/h range for extended submaximal efforts.[5]
- Replace salt. Electrolyte replacement depends primarily on sweat rate, dietary practices, acute consumption, and genetics.
- Attenuate energy deficit (provide calories).
- Be near isotonic. Fluid should have similar concentration of solutes as blood plasma (275-295 mOsm/kg). Drinking a fluid with similar osmotic pressure as body fluids supports body water-electrolyte balance.
- Encourage drinking. Should be tasty enough to make you want to sip. Sipping frequently is better than periodic gulping to maximize fluid and nutrient uptake.
Endurance fuel components and taste
Summary of ingredients of popular endurance fuels and the taste they impart:
Making your own endurance fuel
Weighing the powders: to precisely weigh out powders, you’ll need a digital scale that can measure to the tenths of grams to make individual servings. I find it’s more practical to prepare in larger batches (in which case you can use a food scale to the hundredths). After mixing, place in a large mason jar, shake well and store for later use.
- Electrolytes: Sweating rate and electrolyte concentration in sweat is variable based on physiology, intensity of exercise, and environment. The below table summarizes the main components of sweat on a per liter basis. For the recipe, I selected moderate levels. This endurance fuel, similar to popular products on the market includes major and minor electrolytes, with sodium and chloride the most important. If you’re getting sufficient potassium, calcium, and magnesium from your diet, adding them to your electrolyte is unlikely to provide benefit.
- Carbohydrate (CHO): Glucose, or combinations of glucose + fructose, and sucrose rapidly replace muscle glycogen and maintain blood glucose required for muscle contraction, and support water absorption.[1,7] A good base for long submaximal efforts is 30-50g/hr,[5] supplementing with carbohydrates from food or gels as appropriate. For high intensity efforts, pushing upwards of 100g/hr is possible (with gut training and use of multiple transportable carbohydrates). [6] The recipe uses 70g/L of glucose (resulting in an intake rate of 35g-50g CHO/hr with my estimate total fluid intake rate).
- Caffeine: Caffeine is an established ergogenic aid for sustained endurance exercise, primarily by reducing perception of pain [8,9], enhancing cognitive performance, [10] and increasing time to fatigue in skeletal muscle contraction.[11] Addition of caffeine is entirely optional; a moderate “topping off” dosage for multi-hour events is in the 70-125mg/hr range, with a pre-dosage of 3-6mg/kg BW 30-90 min before event start. Many prefer to supplement with caffeine separately using gels or other means.
- Flavorings: This recipe is fairly tart using 2g of citric acid per liter; adjust this amount up or down to your preference. To change the flavor, Nature’s Flavors powders come in a brilliant variety. For the recipe, I used 2g apple powder which in combination with the citric acid provides a sour apple flavor, much like a Jolly Rancher candy.
Composition and cost comparison
After extensive personal testing on multi-hour training runs in both hot/arid and hot/humid climates and a elevation trail 50K on a hot day, here’s the final comparison. I was still happy drinking it until I finished just under 7 hours later.
If you’re training extensively, you’ll easily save several hundred dollars per year on fuel by making your own. Have fun and reach out anytime if you have questions!
Make your own endurance fuel at ~3x lower cost, with a wide possibility of flavors and customizations. That’s cash towards your next race or investment into training, nutrition, and gear![1] de Oliveira, E.P.; Burini, R.C.; Jeukendrup, A., Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations, Sports Med. 44, S79-85, (2014).
[2] Romijn, J. A.; Coyle, E. F.; et al., Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity. American Journal of Physiology: Endocrinology and Metabolism, 265, E380–E391, (1993).
[3] Jeukendrup, A.; Gleeson, M., Henry. Sports Nutrition, Human Kinetics; 2nd edition (2009).
[4] Smith, J.W.; Bello, M.L.; Ffion, G., A Case-Series Observation of Sweat Rate Variability in Endurance-Trained Athletes, Nutrients, 13, 1807, (2021).
[5] Tiller, N.B.; Roberts, J.D.; 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(1), 50, (2019).
[6] Trommelen, J.; Fuchs, C.J.; et al., Fructose and Sucrose Intake Increase Exogenous Carbohydrate Oxidation during Exercise, Nutrients, 9(2), 167, (2017).
[7] Giso, C.V.; Summers, R.W.; Schedl, H.P.; Bleiler, T.L., Intestinal water absorption from select carbohydrate solutions in humans. J. Appl. Physiol. 73, 2142, (1992).
[8] Laurent. D.; Schneider, K.E.; Prusaczyk, W.K.; et al., Effects of caffeine on muscle glycogen utilization and the neuroendocrine axis during exercise. J Clin Endocrinol Metab, 85, 2170, (2000).
[9] Grossman, A; Sutton, J.R., Endorphins: What are they? How are they measured? What is their role in exercise?, Med Sci Sports Exerc, 17 ,74, (1985).
[10] Ivy, J.L.; Costill, D.L.; et al., Influence of caffeine and carbohydrate feedings on endurance performance. Med Sci Sports Exerc, 11, 6, (1979).
[11] Kalmar, J.M.; Cafarelli, E. Effects of caffeine on neuromuscular function. J Appl Physiol, 87, 801, (1999).
[12] Vitale, K; Getzin, A., Nutrition and Supplement Update for the Endurance Athlete: Review and Recommendations. Nutrients, 11(6), 1289, (2019).
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