What Is the Carbohydrate Intake Requirement for the Ironman?

Tim Podlogar, PhD, is a Research Fellow at the University of Brimingham, Assistant Professor at the University of Primorska (Slovenia), and nutritionist for the Bora Hansgrohe World Tour cycling team. One of Tim's main areas of expertise is the science and practice of carbohydrates in endurance sports, and this is the topic for today's interview.         

IN THIS EPISODE YOU'LL LEARN ABOUT:

-Carbohydrates before, during, and after competition

-When and why to use glucose and fructose

-Is 120 g/h carbohydrate feeding superior to the commonly recommended 90 g/h? 

-Training in a glycogen-depleted state

-Reverse engineering your carbohydrate intake by looking at upcoming workout demands

-Continuous blood-glucose monitoring

-Training the gut

SHOWNOTES:

https://scientifictriathlon.com/tts354/

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LINKS AND RESOURCES:

• Tim's website, Instagram and Twitter
• Nutrition at the cycling World Tour level with Robert Gorgos (Bora-Hansgrohe nutritionist) | EP#267
• RED-S (Relative Energy Deficiency in Sports) with Margo Mountjoy | EP#233
• The menstrual cycle and oral contraception – impact on exercise performance with Kelly McNulty | EP#280
• Carbohydrate intake in racing – a case for going very high with Aitor Viribay Morales (Astana Pro Team) | EP#269
• Musculoskeletal adaptations, “train low” strategies, and muscle fiber types with prof. John Hawley | EP#248
• High carbohydrate, low carbohydrate, or periodised carbohydrate intake with Louise Burke, PhD | EP#236
• High rates of fat oxidation are maintained after the sleep low approach despite delayed carbohydrate feeding during exercise (NB. Delayed feeding in train-low strategies) - Podlogar et al 2021 (full text link)
• Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g h -1 versus 90 g h -1 at different ratios (NB. 90 g/h vs. 120 g/h carbohydrate) - Podlogar et al. 2022
• Progressive increase in glucose transport and GLUT-4 in human sarcolemmal vesicles during moderate exercise (NB. GLUT4 needs time to be translocated to the muscle membrane - reason for progressive feeding) - Kristiansen et al. 1997
• Muscle glycogen utilization during prolonged strenuous exercise when fed carbohydrate (NB. No muscle glycogen sparing with CHO but prolonged endurance -> yet blood CHO source then rescues low muscle glycogen levels -> so 120 might be better than 90 if being able to oxidise it) - Coyle et al. 1986
• Glucose Plus Fructose Ingestion for Post-Exercise Recovery-Greater than the Sum of Its Parts? (NB. Why fructose?) - Gonzalez et al. 2017
• Performance effects of periodized carbohydrate restriction in endurance trained athletes - a systematic review and meta-analysis (NB. review of CHO restriction) - Gejl & Nybo 2021
• Effect of Carbohydrate Content in a Pre-event Meal on Endurance Performance-Determining Factors: A Randomized Controlled Crossover-Trial (NB. Blood glucose rises similarly as lactate on a graded test) - Aandahl et al. 2021
• "Addition of fructose to a carbohydrate-rich breakfast improves cycling endurance capacity in trained cyclists" (NB. Breakfast study) - Podlogar et al. Will be published in the International Journal of Sport Nutrition and Exercise Metabolism.
• Exercise Physiology: Theory and Application to Fitness and Performance - Book by Scott Powers et al. 

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