How to Fuel a Triathlon Brick Session

A brick is where race-day fueling gets honest. Bike legs hide bad plans. The run does not.

If you only practise eating on easy rides, then wonder why T2 feels rough, the gap is usually timing and gut rehearsal, not willpower. This is a practical protocol for athletes and coaches: what to drink on the bike, when a gel still earns a spot, and how to keep the run simple enough that you can repeat it every Saturday.

What a brick is asking of your gut

Classic club brick: solid bike, short transition, then a run that starts harder than your legs want. Heart rate jumps. Blood flow shifts toward working muscle. Stomach comfort shrinks just when you still need carbohydrate arriving.

That is why bricks are the dress rehearsal for race nutrition. You are not just stacking fitness. You are teaching the gut to accept carbs under the same stress pattern as race day.

For distance-specific carb bands once you know the race clock, see sprint and Olympic carbs per hour and 70.3 carbs per hour. This article is about the training session itself.

Lock three numbers before you leave the house

Write them on a bottle or in your session notes:

Carb target once underway (g/h)
Fluid plan (how much you expect to drink on the bike vs run)
Primary delivery (bottle mix, gel, or both)

Useful starting bands for a training brick (after a normal breakfast):

Brick length	Bike carb target	Run carb target	Notes
Short (about 60 to 90 min total)	30 to 60 g/h if the bike is quality work	Often optional sip only	Keep it boring; one product family
Standard club (about 2 to 3 h bike + 20 to 40 min run)	Often 60 to 90 g/h steady	Smaller sips; usually under bike rate	Bike does the fueling work
Long build (3+ h bike + run off)	Often 60 to 90 g/h if gut is trained	Maintain, do not invent a new stack	Same flavours as race week

These are rehearsal targets. Body size, intensity, and gut training move the dial. Use the Fueling Strategy Engine for a session sketch, and the Sweat Rate Estimator if fluid is the part you keep guessing.

Bottle vs gel on the bike

Favour the bottle when: the ride is long enough that you are already drinking; you want carbs and sodium in the same fluid; you hate juggling wrappers at race intensity; or heat is already making the session messier.

Favour a gel (or chew) when: you need a timed hit before a hard interval block; the bottle is water-only for a short quality ride; or that exact gel is already race-rehearsed as a top-up.

Combine when: the bottle carries most of the hourly carbs, and a gel covers a specific moment (pre-T2, late-bike surge, or when bottles run low).

A dual-carb drink mix is built for the bottle job. HYDRAX CORE is one option at 85 g carbs / ~980 mg sodium per serve, mixed in roughly 700 to 1000 ml for a solid bike hour, or slightly more dilute if gut comfort asks for it. Use what you practised.

Gels alone on plain water can work in cool, short bricks. They get clumsy on longer rides when you also need fluid and meaningful sodium in the same hour.

Timing through a bike-then-run brick

A clean template many SEQ club athletes can copy:

Night before / morning: meals you already trust. No new foods on brick morning if this is a race rehearsal.

First 15 to 20 min of the bike: settle in. Small sips. Do not force a full hour of carbs into the warm-up kilometres.

Main bike set: hit your planned g/h. Steady sipping beats one giant gulp every 40 minutes. If you use a full dual-carb serve per hour, match dilution to bottle size so the maths is boring.

Last 10 to 15 min before T2: keep sipping the same product. Avoid a brand-new gel flavour here unless it is already locked for race day. The goal is comfort into the run, not a sugar spike experiment.

Transition: practise what you will do on race day. That might be nothing more than racking the bike and starting the run with the same bottle or soft flask plan.

Run off the bike: smaller sips of the same product family. Do not invent a second sodium system when your legs feel worst. If the run is short (20 to 30 min), many athletes finish on what they took on the bike. If the run is longer, keep the hourly rate lower than the bike and stay consistent.

SEQ heat nod (without rebuilding your summer plan)

Australian bricks in warm months ask more of fluid and sodium than a cool winter ride. You do not need a second article here. Measure sweat once near race conditions, put carbs and sodium in the bottle you are already drinking, and rehearse that dilution. Full heat protocol: Fueling long sessions in Queensland heat.

If last summer left you flat late despite "enough gels," check whether the bottle was carrying real sodium with the carbs, not only sweetness.

Coach-usable brick checklist

Print or paste into the squad notes:

Athlete has a written carb target for bike and for run (separate if needed)
Primary bottle locked (same scoop, same bottle size)
Gel only as rehearsed top-up, not the whole plan
At least two bricks completed at race dilution before key races
No new flavours on the final race-week brick
Sweat rate known roughly if racing in heat (how to measure)
Run plan is simpler than the bike plan on purpose
Athlete can say the plan in one sentence before rolling out

Send athletes the Sweat Rate Estimator and Fueling Strategy Engine once, then make Saturday the dress rehearsal.

Example hour on a standard club brick

Bike hour (steady endurance): about 700 to 1000 ml dual-carb mix aimed at your g/h band; optional gel only if the plan already includes it.

Into T2: same bottle family; no panic salt tabs you have never trained.

Run (20 to 40 min): small sips; finish strong without a second product stack.

If you want one bottle that carries both carbs and sodium for those bike hours, HYDRAX CORE is 85 g carbs / ~980 mg sodium per serve. Adjust dilution after you know your sweat rate and gut response.

Keep brick fueling dull on purpose

The athletes who look organised off the bike usually wrote the numbers down, practised the same bottle on more than one Saturday, and kept the run simpler than the ride. That is the whole game.

Write the plan. Make it boring. Then run it until race week feels ordinary.

Soft next step: try HYDRAX CORE (85 g carbs / ~980 mg sodium per serve) on a training brick, or sketch the session in the Fueling Strategy Engine after you know your sweat rate. For race-distance targets see sprint/Olympic and 70.3. Orders over $95 ship free within Australia.

How to fuel a triathlon brick session: carbs, fluid, timing