Mavr Sports Nutrition Team
Updated September 28, 2026. 10 min read.
A 70.3 race is long enough that nutrition becomes a performance limiter, but fast enough that your stomach can ruin the day if you overdo it.
That is why copying a full Ironman plan usually backfires. You need enough carbohydrate to protect your run, enough sodium and fluid to stay steady, and a plan simple enough to execute when your heart rate is high.
Marathoners have to fuel while running. Triathletes get the bike, where there is less gut jostling and most athletes can take in more. That makes the bike leg the place where you do most of the fueling work. The catch is that the bike is not a buffet: too much fuel, too little water, or drinks that are too concentrated can turn the run into a survival shuffle.
Pre-race breakfast
Carb target1-3g/kg, 2-4 hours before start
Fluid target500-750ml before transition closes
Sodium target300-600mg if you sweat heavily
Bike
Carb target60-90g/hour
Fluid target400-800ml/hour
Sodium target500-900mg/hour
Run
Carb target30-60g/hour
Fluid targetDrink to thirst plus aid stations
Sodium target300-700mg/hour
Post-race
Carb target1-1.2g/kg in first 2 hours
Fluid target150% of fluid lost
Sodium targetInclude sodium with recovery meal
| Race segment | Carb target | Fluid target | Sodium target |
|---|---|---|---|
| Pre-race breakfast | 1-3g/kg, 2-4 hours before start | 500-750ml before transition closes | 300-600mg if you sweat heavily |
| Bike | 60-90g/hour | 400-800ml/hour | 500-900mg/hour |
| Run | 30-60g/hour | Drink to thirst plus aid stations | 300-700mg/hour |
| Post-race | 1-1.2g/kg in first 2 hours | 150% of fluid lost | Include sodium with recovery meal |
These are starting ranges, not commandments. A 58kg athlete racing in cool weather and a 90kg heavy sweater racing in humidity should not use the same plan.
Night before
Main goalTop off carbs with familiar foods
Common mistakeEating a huge, high-fiber dinner
3-4 hours pre-race
Main goalCarb breakfast plus fluids
Common mistakeSkipping breakfast because of nerves
10-15 minutes pre-swim
Main goalSmall carb top-up if practiced
Common mistakeTrying a new gel on race morning
Bike
Main goalMost race carbs, fluids, and sodium
Common mistakeFront-loading too aggressively
Run
Main goalSmaller, frequent carbs and controlled fluids
Common mistakeTrying to fix bike underfueling all at once
| Timing | Main goal | Common mistake |
|---|---|---|
| Night before | Top off carbs with familiar foods | Eating a huge, high-fiber dinner |
| 3-4 hours pre-race | Carb breakfast plus fluids | Skipping breakfast because of nerves |
| 10-15 minutes pre-swim | Small carb top-up if practiced | Trying a new gel on race morning |
| Bike | Most race carbs, fluids, and sodium | Front-loading too aggressively |
| Run | Smaller, frequent carbs and controlled fluids | Trying to fix bike underfueling all at once |
Your pre-race breakfast should top up glycogen without leaving food sitting in your stomach during the swim. Keep it familiar, carb-focused, and low in fat and fiber.
Most athletes underfuel the bike because they feel fine early. Then they reach the run with low glycogen, rising core temperature, and a stomach that no longer wants concentrated gels.
The bike is your best fueling window. You are seated, impact is lower, and you can carry bottles, gels, chews, or solids. Use that advantage.
2:30 bike
Carbs to carry150-225g total
Simple setupTwo carb bottles plus 2-3 gels
3:00 bike
Carbs to carry180-270g total
Simple setupTwo carb bottles, gels, and aid-station backup
3:30 bike
Carbs to carry210-315g total
Simple setupConcentrated bottle plus water, gels, and sodium plan
| Bike split | Carbs to carry | Simple setup |
|---|---|---|
| 2:30 bike | 150-225g total | Two carb bottles plus 2-3 gels |
| 3:00 bike | 180-270g total | Two carb bottles, gels, and aid-station backup |
| 3:30 bike | 210-315g total | Concentrated bottle plus water, gels, and sodium plan |
If you are new to high carb intake, start around 60-75g per hour on the bike and build toward 90g per hour only as your gut tolerates it. The higher end usually needs gut training and products that combine glucose and fructose.
The half-marathon run is where athletes discover whether their bike fueling worked. If you arrive depleted, the run becomes survival. If you arrive overfed, the run becomes a GI problem.
Cool conditions
Gels or chews every 25-35 minutes with water, adjusted to pace.
Hot conditions
Put cooling and fluid access first while keeping carb intake steady.
Nausea starting
Slow intake briefly, rinse your mouth, sip water, then resume with smaller carb doses.
Energy fading
Take fast carbs with water and avoid stacking several concentrated products.
| Run scenario | Fueling approach |
|---|---|
| Cool conditions | Gels or chews every 25-35 minutes with water, adjusted to pace. |
| Hot conditions | Put cooling and fluid access first while keeping carb intake steady. |
| Nausea starting | Slow intake briefly, rinse your mouth, sip water, then resume with smaller carb doses. |
| Energy fading | Take fast carbs with water and avoid stacking several concentrated products. |
Your long rides and brick workouts are not just fitness sessions. They are nutrition rehearsals.
A 70.3 fueling plan only works if it is concrete enough to follow at mile 40 with a tired brain. Do the math in advance and write it on a card taped to your top tube: total carbs to take on the bike, when each bottle and gel goes down (for example, a gel every 30 minutes and a few sips of carb drink every 15), your per-hour sodium, and the first run gel timed for 10 minutes into the run. Estimating your splits gives you the race duration, which gives you the totals — and once it is on the card you are executing a plan, not doing arithmetic with depleted legs.
Estimating race duration from your splits and turning it into per-segment carb, sodium, and fluid targets is precisely the calculation Mavr runs for you, then carries into your training-day macros. But the deliverable is that little card, and you can build it yourself from the numbers in this guide.
Most athletes should start with 60-90g carbs per hour on the bike and 30-60g per hour on the run. The bike target is higher because digestion is easier with less impact. Practice these targets in training before race day.
Some athletes tolerate small solid foods early on the bike, but gels, chews, drink mix, and simple low-fiber options are usually safer. Avoid solid food late on the bike and during the run unless you have practiced it repeatedly.
Maybe. Heavy sweaters and hot races often require more sodium than standard sports drink provides. Start with 500-900mg sodium per hour on the bike and adjust based on sweat rate, conditions, and GI tolerance.
Common causes include too much fuel late on the bike, drinks that are too concentrated, dehydration, heat stress, high intensity, or a product you have not practiced. Brick sessions are the best place to find which one it is.
Yes. Mavr supports endurance athletes who train across swim, bike, run, strength, and recovery days, then adjusts nutrition targets around the actual workload instead of giving one flat calorie target.
General guidance for healthy adults, not medical advice. Talk to a doctor or registered dietitian if you have a health condition, take medicines or have special dietary needs.
Stop building your 70.3 plan from forum guesses. Use Mavr to create a fueling timeline for your actual race, body, and training block.
Ask Kai, the coach in the app