Triathlon nutrition: managing the three legs and transitions
Triathlon is a unique discipline where nutrition is famously dubbed the 'fourth leg'. Combining swimming, cycling, and running imposes major physiological and logistical constraints. Swimming prevents any fuel intake, cycling is the golden window for high carbohydrate intake (up to 90 g/h), and running severely stresses the stomach, requiring lighter and more fluid fueling. This guide presents a complete protocol to structure your intake across legs and manage transitions smoothly.
Before the race: load and swim start
In the days leading up to the race, maximize glycogen stores (8 to 10 g/kg/day of simple carbs). On race morning, eat a digestible meal 3 hours before the start, then sip an electrolyte drink until 30 minutes before warm-up. As swimming is a phase of potential gastric reflux, avoid taking a gel right before entering the water.
During: swim, bike, transitions and run
During the race, split your strategy into three parts. Swim: no fuel. T1: rinse your mouth and take a small sip of fresh water to wash away salt or chlorine. Bike: the golden window. Use the stable position to target high carb intakes (60 to 90 g/h) using a mix of energy drink and digestible solids (bars, chews) early on, shifting to gels late in the ride. T2: a sip of water. Run: your stomach takes a beating. Switch to 100% liquid or semi-liquid fuel (gels washed down with water, or aid-station drink) and lower your carb target (40 to 60 g/h) if needed to keep your GI tract happy.
Your fuelling timelines
Fueling plan — Half-Ironman Triathlon (target 5 h)
Before: H-3 meal + light pre-start electrolyte drink
Bike: maximum intake (70-80 g/h) + 600-750 ml/h
Run: moderate liquid/semi-liquid intake (40-50 g/h)
White bread + honey + banana
500 ml water + electrolytes
Rinse mouth with water
Small sip if needed
First sips of energy drink
(sip continuously from bottle)
Digest-friendly energy bar
+ water from 2nd bottle
Continue sipping energy drink
Standard energy gel
+ water
Sip of fresh water
Standard energy gel
+ water from aid station
Caffeine gel (75 mg)
+ water
Energy chews / gummies
Recovery drink
Protein + carbs + sodium
On the bike, use flat sections to fuel regularly.
After: recovering from a triple effort
Immediately after the finish, start by replacing lost fluids and sodium. Within 30 minutes, consume a recovery drink containing proteins for muscle repair and carbs to reload glycogen. Eat a complete, salted meal as soon as possible.
Practical checklist
- Active carb loading over the 2-3 days prior
- Proven pre-race meal eaten 3 hours before start
- Bike plan: energy bottles + gels/bars ready (60-90 g/h)
- Run plan: easy-to-open gels + water at each aid station
- Salt pills or electrolyte capsules ready if hot weather is expected
Common mistakes
- Neglecting to fuel on the bike because the run feels far away
- Taking hard or solid foods during the run leg
- Skipping hydration and sodium on the bike because the weather feels cool
- Drinking only plain water on efforts lasting over 4 hours, risking hyponatremia
- Trying an unknown sports drink provided at aid stations
FAQ
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