Sodium target: 700 mg/hour (2708 mg total)
- Moderate risk: combine sports drink with salt tablets, often about 250 mg sodium each.
- < 60 minutes: water is usually enough; carbs are optional.
- 60-150 minutes: 30-60 g carbs per hour, roughly a gel plus a banana.
- > 150 minutes: marathon-level efforts can train toward 60-90 g/hr with gut tolerance practice.
- Fluids: 150-200 ml every 15-20 minutes; avoid large boluses that upset the stomach.
- Sodium: heavy sweaters can lose 1000 mg+ per hour, especially in heat.
- Practice fueling: test everything in long runs; do not try new fuel on race day.
Sources:ACSM, Running Biji MET calculation
Glucose uses SGLT1 transporters, which saturate at about 1 g/min. Excess carbs can pull water into the intestine and cause GI distress.
Jeukendrup (2010) showed that fructose uses the independent GLUT5 pathway, increasing total absorption by roughly 50-75%.
Viribay et al. (2020, Nutrients) studied 120 g/h in ultra-trail athletes and reported better finish times and lower muscle-damage markers. It requires 4-8 weeks of gut training.
For events under 60 minutes, holding carbs in the mouth for 5-10 seconds may activate reward pathways and improve performance 2-3% without swallowing.
Sources: Jeukendrup 2010 (PubMed), Stellingwerff & Cox 2014, Viribay 2020 (120g/h), Carter 2004 (mouth rinse)
- Exercise-associated hyponatremia (EAH): Almond et al. (2005, NEJM) found meaningful risk in marathon settings.
- Risk factors: drinking more than sweat rate, race duration over 4 hours, female sex, and slower finish times.
- Principle: drink to thirst instead of forcing fluid every 15 minutes.
- Measure sweat rate: weigh before and after a long run; about 1 kg loss equals 1 L fluid.
- Sodium helps: salt plus electrolyte drink supports hydration and lowers hyponatremia risk.
Sources: Almond et al. 2005 NEJM, 2015 EAH Consensus Statement
Train-Low: easy or long runs with intentionally lower carbohydrate availability can stimulate fat oxidation and mitochondrial adaptations.
Train-High: interval, tempo, and race-pace sessions should be fueled well; underfueling quality work lowers output and raises stress.
Practical rule: fuel quality, be selective with low-carb easy volume. Race day and the final 24-48 hours before racing should be Train-High.