Two of the best triathletes on the planet came undone in the Kona heat in back-to-back years, so how do you fuel a hot race without falling apart on the run?

After two decades of working with triathletes, I can tell you that most hot races are won or lost before the gun even goes off. As an age-grouper you’re out on course for hours longer than the pros, in the hottest part of the day, often on a race nutrition plan you built and tested through winter. I break down what the heat actually does to your body, why falling apart in a hot race comes down to much more than toughness and what should change in your plan when the forecast says it’s going to be a scorcher.

WHAT YOU’LL LEARN

• Why your body burns through stored carbohydrate faster in the heat, and why your aid stations can only top up so much
• The 3 ways triathletes fall apart in a hot race that look identical from the side of the road, and why they need opposite fixes
• Why “it’s hot, drink more” is the advice that puts age-groupers in the medical tent
• What heat does to your gut, and why backing off your fuel can make it worse
• The 4 mistakes I see over and over when the forecast is hot
• How one of my Academy athletes went from walking between poles at Spudman to crossing the line at the 70.3 World Championship in Nice

TIMESTAMPS

00:00 Introduction
01:28 How heat changes your body's job
03:30 3 ways to fall apart in a hot race
07:03 Why your gut struggles in the heat
09:16 4 mistakes when the forecast is hot
13:08 How to prepare for a hot race

STUDIES MENTIONED

• Almond, C. S. D., Shin, A. Y., Fortescue, E. B., Mannix, R. C., Wypij, D., Binstadt, B. A., Duncan, C. N., Olson, D. P., Salerno, A. E., Newburger, J. W., & Greenes, D. S. (2005). Hyponatremia among runners in the Boston Marathon. New England Journal of Medicine, 352(15), 1550–1556. https://doi.org/10.1056/NEJMoa043901
• González-Alonso, J., Teller, C., Andersen, S. L., Jensen, F. B., Hyldig, T., & Nielsen, B. (1999). Influence of body temperature on the development of fatigue during prolonged exercise in the heat. Journal of Applied Physiology, 86(3), 1032–1039. https://doi.org/10.1152/jappl.1999.86.3.1032
• Hew-Butler, T., Rosner, M. H., Fowkes-Godek, S., Dugas, J. P., Hoffman, M. D., Lewis, D. P., Maughan, R. J., Miller, K. C., Montain, S. J., Rehrer, N. J., Roberts, W. O., Rogers, I. R., Siegel, A. J., Stuempfle, K. J., Winger, J. M., & Verbalis, J. G. (2015). Statement of the Third International Exercise-Associated Hyponatremia Consensus Development Conference, Carlsbad, California, 2015. Clinical Journal of Sport Medicine, 25(4), 303–320. https://doi.org/10.1097/JSM.0000000000000221
• Jentjens, R. L. P. G., Wagenmakers, A. J. M., & Jeukendrup, A. E. (2002). Heat stress increases muscle glycogen use but reduces the oxidation of ingested carbohydrates during exercise. Journal of Applied Physiology, 92(4), 1562–1572. https://doi.org/10.1152/japplphysiol.00482.2001
• McCubbin, A. J., Allanson, B. A., Caldwell Odgers, J. N., Cort, M. M., Costa, R. J. S., Cox, G. R., Crawshay, S. T., Desbrow, B., Freney, E. G., Gaskell, S. K., Hughes, D., Irwin, C., Jay, O., Lalor, B. J., Ross, M. L. R., Shaw, G., Périard, J. D., & Burke, L. M. (2020). Sports Dietitians Australia position statement: Nutrition for exercise in hot environments. International Journal of Sport Nutrition and Exercise Metabolism, 30(1), 83–98. https://doi.org/10.1123/ijsnem.2019-0300
• Mougin, L., Macrae, H. Z., Taylor, L., James, L. J., & Mears, S. A. (2025). The effect of heat stress and dehydration on carbohydrate use during endurance exercise: A systematic review and meta-analysis. Sports Medicine, 55(11), 2825–2847. https://doi.org/10.1007/s40279-025-02294-3
• Parkin, J. M., Carey, M. F., Zhao, S., & Febbraio, M. A. (1999). Effect of ambient temperature on human skeletal muscle metabolism during fatiguing submaximal exercise. Journal of Applied Physiology, 86(3), 902–908. https://doi.org/10.1152/jappl.1999.86.3.902
• Périard, J. D., Racinais, S., & Sawka, M. N. (2015). Adaptations and mechanisms of human heat acclimation: Applications for competitive athletes and sports. Scandinavian Journal of Medicine & Science in Sports, 25(S1), 20–38. https://doi.org/10.1111/sms.12408
• Roberts, W. O., Armstrong, L. E., Sawka, M. N., Yeargin, S. W., Heled, Y., & O’Connor, F. G. (2021). ACSM expert consensus statement on exertional heat illness: Recognition, management, and return to activity. Current Sports Medicine Reports, 20(9), 470–484. https://doi.org/10.1249/JSR.0000000000000878
• Snipe, R. M. J., Khoo, A., Kitic, C. M., Gibson, P. R., & Costa, R. J. S. (2017). Carbohydrate and protein intake during exertional-heat stress ameliorates intestinal epithelial injury and small intestine permeability. Applied Physiology, Nutrition, and Metabolism, 42(12), 1283–1292. https://doi.org/10.1139/apnm-2017-0361
• Snipe, R. M. J., Khoo, A., Kitic, C. M., Gibson, P. R., & Costa, R. J. S. (2018). The impact of exertional-heat stress on gastrointestinal integrity, gastrointestinal symptoms, systemic endotoxin and cytokine profile. European Journal of Applied Physiology, 118(2), 389–400. https://doi.org/10.1007/s00421-017-3781-z
• Speedy, D. B., Noakes, T. D., Rogers, I. R., Thompson, J. M. D., Campbell, R. G. D., Kuttner, J. A., Boswell, D. R., Wright, S., & Hamlin, M. (1999). Hyponatremia in ultradistance triathletes. Medicine & Science in Sports & Exercise, 31(6), 809–815. https://doi.org/10.1097/00005768-199906000-00008
• van Wijck, K., Lenaerts, K., Grootjans, J., Wijnands, K. A., Poeze, M., van Loon, L. J. C., Dejong, C. H. C., & Buurman, W. A. (2012). Physiology and pathophysiology of splanchnic hypoperfusion and intestinal injury during exercise: Strategies for evaluation and prevention. American Journal of Physiology: Gastrointestinal and Liver Physiology, 303(2), G155–G168. https://doi.org/10.1152/ajpgi.00066.2012

RESOURCES MENTIONED

• Ep 214: Sweat Science
• Ep 251: How Do You Carb Load for a Triathlon Without Feeling Bloated and Heavy?
• Ep 253: Is Carb Loading a Myth?

START YOUR HOT RACE WITH A FULL FUEL TANK

If you have a hot race coming up in the next 12 months, the fuel tank you take to the start line is your buffer. My Carb Loading Masterclass shows you exactly how much carbohydrate to eat, when to eat it and what to eat, so you can carb load properly without feeling heavy and bloated. Get the Carb Loading Masterclass

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