120 g/hr carbohydrate improves running economy in elite marathoners 📈
Science now matching practice.
¹³C labelled glucose-fructose show greater exogenous and whole-body CHO oxidation and lower O₂ cost of running at 120 vs 60 & 90 g·h⁻¹ in elite male marathoners
Study Details
This new study recruited 8 elite (sub 2:30:00) male marathon runners to a randomised crossover study consisting of 3 x 120-min running trials 🏃♂️
Consuming either…
1️⃣ 60 g/hr
2️⃣ 90 g/hr
3️⃣ 120 g/hr
Participants ate a standardised diet the day prior to testing at 8 g/kg carbs (2 g/kg protein + 1 g/kg fat) 🍞
Plus a standardised pre-test breakfast 2-hr prior containing; 2 g/kg carbs and minimal fat / protein ⏰
Here is what they found ⬇️
Key Findings
Mean whole body carb oxidation (g/min) =
120 g/hr ➡️ 3.06 ± 0.19
90 g/hr ➡️ 2.46 ± 0.12
60 g/hr ➡️ 2.08 ± 0.03
Mean exogenous carb oxidation (g/min) =
120 g/hr ➡️ 1.68 ± 0.16
90 g/hr ➡️ 1.31 ± 0.18
60 g/hr ➡️ 0.89 ± 0.11
👉Across all trials: 120 g/hr > 90 g/hr > 60 g/hr
Running economy was also significantly improved in the 120 g/hr condition 🫁
(2.6% lower oxygen cost vs 60 g/hr)
Gastrointestinal symptoms were high in all conditions but highest in 120 g/hr 😮💨
Conclusion
A high carb ingestion of 120 g/hr provides a metabolic advantage to elite marathon runners by improving…
✅ Whole body carb oxidation
✅ Exogenous carb oxidation
✅ Running economy
Although gut training strategies are required to minimise gut issues with this level of fuelling ⚠️
Reference
https://journals.physiology.org/doi/abs/10.1152/japplphysiol.00665.2025
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