Race Fueling
Triathlon Nutrition: The Brick Workout Fueling Strategy
Brick workouts are hard enough without an upset stomach. Learn how to fuel the bike-to-run transition so you can actually run off the bike.
Quick answer
Fuel brick workouts by taking 30–60 g carbs/hour on the bike, exit the bike with topped-off glycogen, and transition to gels and drinks on the run.
You've heard the expression: "Run off the bike."
What they don't tell you is that how you fuel the bike determines whether you can actually run.
Too many athletes crush the bike leg, hop off, and immediately feel like they're running in quicksand. The problem isn't their legs — it's their glycogen stores and hydration balance.
Why Brick Workouts Break You
During the bike leg:
- You deplete muscle glycogen faster than you realize
- Your legs feel fine because you're not bearing weight
- Hydration shifts occur as blood pools in your legs
- Sodium levels drop as you sweat in the aero position
When you start running:
- Your muscles need glycogen immediately
- Your cardiovascular system is already taxed
- Your stomach may be sloshing from bike fueling
- Your brain is foggy from effort and possible dehydration
Result: the dreaded "dead legs" feeling in the first mile of the run.
The Bike Fueling Strategy
The goal is to finish the bike with glycogen stores intact and hydration balanced. Here's how:
- Target 60–90 g carbs/hour on the bike (race distance dependent)
- Sip a carb-electrolyte drink continuously
- Take 1–2 gels during the bike (every 30–45 minutes)
- Stay ahead of thirst — don't wait to drink
- Adjust for heat: more fluids, more sodium
Distance-Specific Plans
| Distance | Bike Duration | Carbs During Bike | Key Strategy |
|---|---|---|---|
| Sprint | 45–60 min | 30–45 g | Sip drink, optional gel |
| Olympic | 2–2.5 hrs | 60–90 g | Full drink + 2 gels |
| Half Ironman | 3–4 hrs | 90–120 g | Multiple bottles, solids if tolerated |
| Ironman | 5–7 hrs | 150–210 g | Max absorption, alternate sources |
The Transition: Bike to Run
The first 10 minutes off the bike are critical. Your strategy:
- Grab a gel or chews as you transition (20–30 g quick carbs)
- Sip water or sports drink while running
- Start slow — your legs need 5–10 minutes to adjust
- Don't sprint out of transition; pace is everything
Pro tip: Practice this transition in every brick workout so your gut learns what to expect.
Run Fueling After the Bike
Once you're running:
- Continue 30–60 g carbs/hour (gels, drink mix, chews)
- Sip fluids at every aid station
- Take sodium if you're sweating heavily
- Adjust based on how you feel — listen to your body
Brick Workout Example: Olympic Distance
Here's a complete nutrition plan for a 90-minute bike + 5K run brick:
| Time | Activity | Fuel | Carbs |
|---|---|---|---|
| Pre-workout | Transition area | Banana + water | 25 g |
| Bike 0–30 min | Easy spin | Sip carb drink | 15 g |
| Bike 30–60 min | Build effort | Gel + drink | 35 g |
| Bike 60–90 min | Race pace | Second gel + drink | 35 g |
| Transition | T1 to T2 | Quick gel as you run | 25 g |
| Run 0–3K | Settle in | Sip water, hold pace | 0 g |
| Run 3–5K | Push to finish | Gel if needed | 25 g |
Total: ~160 grams of carbs over 90 minutes of cycling + 30 minutes of running.
Common Brick Workout Mistakes
- Underfueling on the bike because it feels easy
- Drinking only water and diluting sodium
- Taking a gel 5 minutes before the run starts (GI distress)
- Sprinting out of transition
- Not practicing the transition with real nutrition
Rehearse the Transition, Not Just the Distance
The brick exists to rehearse the one moment a race can fall apart: the bike-to-run transition. Treat every brick as a full nutrition dress rehearsal. Fuel the bike properly so you start the run topped up — most athletes under-fuel the bike because it feels easy — take your last gel 5-10 minutes before you rack, not as you start running, and ease into the first kilometer of the run rather than sprinting out of T2 on a stomach that is still catching up. Do that on every brick and race day becomes a repeat of something your gut already knows.
Building the phase-by-phase carb and hydration targets for your specific race distance is something MAVR can generate for you, but the habit of rehearsing the transition with real nutrition is the part that actually pays off on race day.
Own your bike-to-run transitions.
Frequently Asked Questions (FAQ)
Can I take a gel right before I start running?
No. Take gels 5–10 minutes before transition so they've partially digested. Taking one right before running often causes cramping.
What about caffeine in a brick workout?
Caffeine can help with mental focus and performance. Try a caffeinated gel mid-bike or early in the run.
How do I practice brick nutrition?
Do every brick workout with race-day nutrition. Your gut needs to learn what to expect under fatigue.
Does MAVR help with triathlon nutrition?
Yes. Enter your race distance and MAVR builds phase-by-phase nutrition plans for swim-bike-run.
Written by
MAVR Sports Nutrition Team
The MAVR sports-nutrition team translates peer-reviewed endurance research (Jeukendrup, Burke, the ISSN) into daily fueling for runners and triathletes.