Most triathletes have a swim plan, a bike plan, and a run plan. Almost nobody has a T1 or T2 plan. The transitions are the cheapest place to win five minutes in a 70.3 — and the most expensive place to lose your race when you arrive at the run with a stomach full of half-digested gel and no fuel since aid station four. Here is the protocol.

The one-sentence answer

T1: small sip of sports drink if transition is longer than three minutes; do not force solid carbs after the swim. T2: drop solids 60 minutes before T2, and take a gel + water in transition if your last fuel was more than 20 minutes ago.

Why transitions matter

Each transition triggers two physiological hits: an abrupt postural change (horizontal swimming to vertical biking, or biking to running) and a brief heart-rate spike from accelerated transition pace. Both shift blood flow away from the gut. Fuel that lands during a transition often does not absorb until 5–10 minutes into the next leg — so timing it wrong stacks unabsorbed carb in the stomach during the worst possible window.

T1 — coming off the swim

After 25–60 minutes in the water, your gut has been compressed by prone positioning and chilled by water temperature. You may have swallowed water and salt. The autonomic nervous system has been in relative parasympathetic mode for an hour. None of this is friendly to solid carbs.

If T1 is under 3 minutes: skip fueling in T1, take your first carb 5–10 minutes onto the bike when the gut has warmed up.

If T1 is 3–10 minutes: small sip of sports drink (≈100–200 mL) on the bike rack. Do not eat solids in T1.

Saltwater swim: add a salt tablet on the bike rack — you have ingested 200–600 mg of sodium without water, which can mask early dehydration once you start sweating on the bike. See our electrolytes guide for personalised targets.

The bike — leading into T2

The biggest mistake on a triathlon bike is fueling on solids right up to T2. Solid food (bars, bananas, sandwiches) takes 60–90 minutes to clear the stomach. Eating one 30 minutes before T2 means you arrive at the run with food still in transit — the most reliable way to bonk on the run.

Drop solids 60–90 minutes before the bike-to-run transition. Switch to liquid carbs (sports drink, gels with water). Land in T2 with the stomach mostly clear. See bike-vs-run carb targets in our 70.3 fueling guide and Ironman 140.6 fueling guide.

T2 — onto the run

The bike-to-run transition is where most race-ending GI episodes start. The shift from leaning on aero bars to upright running compresses the gut from a different angle, and the impact of running shakes anything unabsorbed.

If you fueled in the last 15 minutes of the bike: nothing in T2. First gel at minute 10–15 of the run.

If your last fuel was 20+ minutes ago: gel + 100 mL of water on the run-out, walking the first 30 seconds while it settles.

If T2 is long (3+ minutes): salt tab + a few sips of water. No solids.

Hot-weather variant

In heat, gut-shutdown risk is dramatically higher. Drop bike solids earlier — 90+ minutes before T2 instead of 60. Use cold sponges over the gut on the bike to ease gastric blood flow. Detailed protocol in our hot-weather marathon fueling guide — the principles transfer directly to triathlon.

70.3 vs 140.6

70.3: the bike is 2–3 hours; you can run liquid-only end to end. Solids optional; many top-of-pack athletes skip them entirely.

140.6: 5–7 hours on the bike requires solids in the middle third (boiled potatoes, energy bars, real food) to prevent palate fatigue, but switch off solids 60–90 minutes before T2 just like a 70.3.

The aid-station strategy on the run

Walk every aid station for the first 30 seconds — sip, swallow, then run. The 30-second pace cost is invisible by mile 10; the benefit of actually absorbing fuel rather than spilling it down your shirt is enormous. The same applies to stand-alone marathons.

Practise the transitions

Run two or three brick workouts (bike-to-run) at race pace with full fueling protocol in the final 4 weeks before race day. Trying any of the above for the first time on race day is the highest-variance decision in triathlon — see our gut training guide for the broader gut-prep arc.

Frequently asked questions

Should I eat in transition or skip it? Skip unless transition is unusually long. The next 10 minutes of cycling or running is a better place to refuel.

Salt tab at T1? Yes if you swallowed seawater or sweat heavily on the warm-up.

Coffee gel at T2? Useful for back-half lift on long days — see our caffeine strategy guide for timing.

What about porta-potty timing? If you need it, take it in T2. Cost: 2–3 minutes. Cost of not taking it: bonking at mile 6 of a half marathon.