Most age-group Ironman athletes lose their race on the bike — not because they were too slow, but because they were too strong. They ride 78% of FTP for five hours, arrive at T2 with quads that won't absorb landing forces, and walk the second half of the marathon wondering what went wrong.
The bike leg of an Ironman is not a 180km time trial. It is a pacing exercise that protects the run. That single shift in framing changes how you structure the whole 16-week build.
This plan is the one we use with age-group athletes inside our triathlon bike coaching programme, stripped down to its spine. Three phases, seven to fourteen hours a week, with explicit guardrails to keep the run alive.
Who this plan is for
This is a 16-week plan for age-group athletes targeting a full-distance Ironman, with at least 12 months of consistent endurance training behind them. If you are coming off a half-distance race or a strong winter base, you are in the right place. If you are training for your first triathlon of any kind, this is too much volume too fast.
The target athlete rides 3–5 times per week, has a reliable FTP number from the last eight weeks, and can currently complete a 3-hour ride without falling apart. Weekly training time sits between 8 and 14 hours across swim, bike, and run. Peak weeks touch 14–15 hours. That is the ceiling for most working age-groupers with families — not because more wouldn't help in a vacuum, but because the recovery debt becomes unmanageable.
Joe Friel has made this point repeatedly on the Roadman Cycling Podcast: the athletes who improve year on year are the ones who finish each training block healthy, not the ones who survive the biggest week. Consistency beats heroics across a 16-week arc.
If you don't have a current FTP, test in week 1 using a 20-minute protocol or a ramp test. Build your FTP zones from that number and retest in week 7. Every session in this plan is prescribed relative to FTP, so the number has to be honest. Overstated FTPs produce undercooked sessions and sandbagged race days.
Finally, this plan assumes you have a time-trial bike or a road bike with clip-on bars, and that you are spending meaningful time in your race position from week 1. Position-specific endurance is non-negotiable — it is not something you can bolt on in the final month.
Phase 1: Base endurance (weeks 1–6)
Phase 1 builds the aerobic chassis. Every session lives at 65–75% of FTP, with the majority sitting squarely in Zone 2. This is the phase where most age-groupers get impatient and ruin their year.
Prof. Stephen Seiler's polarised work shows that 75–80% of endurance training volume should sit below the first lactate threshold. For most age-groupers, that means conversational pace where you can speak in full sentences. If you are grinding out Zone 3 tempo four days a week, you are building a ceiling instead of a floor.
A typical Phase 1 week looks like this: Tuesday, 75-minute ride with 3x12 minutes at 75% of FTP; Thursday, 60 minutes easy with cadence drills; Saturday, long ride building from 2h30 in week 1 to 4h00 in week 6; Sunday, 90 minutes Zone 2 off the previous day's load. Total bike time: 6–8 hours. Total training time: 9–12 hours including swim and run.
The long ride is the anchor. Steady power, steady heart rate, strict fuelling practice. Use every weekend ride to rehearse race nutrition — this is not the time to "see how you feel" without calories. Aim for 80g of carbohydrate per hour from week 3 onwards.
Week 4 is a recovery week. Cut volume by 40% and hold intensity. Week 4 is not a rest week — it is an adaptation week where the fitness you built in weeks 1–3 consolidates. Skip it and you arrive at week 7 flat.
By the end of week 6, a benchmark 3-hour ride at 70% of FTP should feel controlled, with heart rate drift under 5% across the full duration. If heart rate is climbing 10+ bpm over three hours at steady power, your aerobic base isn't ready for Phase 2 and you need a two-week extension.
Phase 2: Race-specific power (weeks 7–12)
Phase 2 is where the plan gets specific to Ironman demands. The emphasis shifts from pure aerobic base to sustained sub-threshold work in your race position, combined with longer rides that simulate race-day fuelling load.
Retest FTP at the start of week 7. Update your zones. The key session in this phase is the sweet spot long interval — 2x30 minutes or 3x20 minutes at 85–88% of FTP, performed on the TT bike in full aero position. This session trains the specific fatigue profile you meet at hour four of an Ironman, when your lower back and hip flexors are the limiters, not your cardiovascular system.
Dan Lorang's approach with his World Tour and Ironman athletes leans heavily on this kind of specificity. The stimulus is not just metabolic — it is positional, neuromuscular, and mental. You are teaching the body to produce race power in race posture for race duration.
A typical Phase 2 week: Tuesday, 90-minute sweet spot session (3x20 at 85% FTP); Thursday, 75 minutes with race-pace efforts (2x45 minutes at 72% FTP); Saturday, long ride 4h30–6h00 with race-pace blocks; Sunday, 2-hour Zone 2 with brick run off the bike. Total bike time: 8–10 hours. Total training time: 12–15 hours.
The long ride in Phase 2 includes 60–90 minutes of continuous riding at goal race power, usually in the middle third of the ride. Start the ride aerobically, execute the race-pace block cleanly, then ride the final hour steady. This rehearses the exact demand of race day.
Week 10 is another recovery week. Weeks 11 and 12 are the biggest weeks of the plan — peak volume, peak specificity. The week 12 long ride of 5.5–6 hours is the capstone session. Execute it at race intensity with race fuelling and race kit. If this ride goes well, your race is largely written.
Two brick runs per week in Phase 2, one short off Tuesday's sweet spot (15 minutes at marathon pace plus 30 seconds) and one longer off Sunday's Zone 2 ride (45–60 minutes progressive). These are not extra work — they are the bridge between bike fitness and run capacity.
Phase 3: Taper and sharpen (weeks 13–16)
Taper is where age-groupers panic and undo months of work. The temptation to "get one more long ride in" or "test the legs" is the single most common cause of flat race-day performance. Resist it.
Week 13 drops volume by 25% and holds intensity. You still do the Tuesday sweet spot session, still do a long ride (but only 4 hours), still do the brick work. This is not a rest week. It is a sharpening week where accumulated fatigue begins to lift.
Week 14 drops volume another 20%. The long ride becomes 3 hours, but includes a 45-minute race-pace block. Intensity stays high; duration drops. You should start feeling unusually fresh by the end of this week, which many athletes misread as a signal to train harder. Don't.
Week 15 is the true taper week. Total bike time drops to 4–5 hours. Sessions are short and sharp: 60-minute rides with 6x3 minutes at 95% of FTP, 45-minute Zone 2 spins, one 2-hour ride on Saturday with a 20-minute race-pace block. The goal is to keep the neuromuscular system alert without accumulating fatigue.
Race week is a standard 7-day taper. Monday off or easy swim. Tuesday 45 minutes with 3x3 minutes at race power plus 5%. Wednesday 30 minutes easy. Thursday 30-minute bike spin with 2x1 minute race pace. Friday rest or 20-minute shake-out. Saturday 20 minutes easy plus short transition rehearsal.
John Wakefield has talked on the podcast about how Red Bull-Bora-Hansgrohe periodise their taper around freshness markers, not around a fixed template. The principle carries over: if your resting heart rate is elevated or HRV is suppressed in week 15, reduce further. If you feel flat in week 14, that is normal — supercompensation arrives in the final 7–10 days.
Don't train through doubt in taper. The fitness is built.
Key weekly sessions explained
Five sessions carry the plan. Every week contains some combination of these, scaled by phase.
The Zone 2 long ride. 3–6 hours at 65–72% of FTP. Conversational, steady, fuelled. This is 50–60% of your weekly bike volume and the single most important session in the plan. Do not let it drift into Zone 3. If your heart rate creeps, slow down. The adaptation you want — capillary density, mitochondrial density, fat oxidation rate — only develops below threshold.
The sweet spot session. 2x20 to 3x25 minutes at 85–90% of FTP. Builds sustainable power and positional endurance. Always performed in race position on the TT bike from week 5 onwards. This is the session that translates most directly to race-day bike split.
The race-pace block. 45–90 minutes continuous at 68–72% of FTP, embedded within a longer ride. Looks easy on paper. Feels deceptively hard in hour three of a five-hour ride. This teaches the body and mind what Ironman race power actually feels like when you are half-fuelled and fatigued.
The VO2 sharpener. 5x3 to 6x3 minutes at 110–120% of FTP. Used in Phase 2 and race week only. One per week maximum. Keeps the top end sharp without adding the fatigue cost of heavy threshold work. Dan Bigham has pointed out that even for pure endurance events, small doses of high-end work preserve neuromuscular power and efficiency at submaximal intensities.
The brick run. 15–60 minutes off the bike at marathon pace plus 30–60 seconds. Teaches the transition feel, tests fuelling carry-over, builds run-specific resilience. Schedule 4–6 across the plan, concentrated in Phase 2. Not every weekend.
For in-ride pacing and intensity distribution, check your numbers against your FTP zones before each key session. Prescribed percentages only work if the underlying FTP is current.
Fuelling the long rides
Under-fuelling is the second most common cause of age-group Ironman failure, right after over-biking. The two are linked: athletes who can't absorb calories end up riding easier than planned and running worse than planned.
Current sports nutrition research, including work Tim Spector has discussed on the podcast around metabolic flexibility, supports carbohydrate intakes of 80–120g per hour for long-duration efforts. The upper end of that range requires a trained gut. That training happens in weeks 1–12, not on race day.
Start Phase 1 at 60g per hour. Build to 80g per hour by week 4. Aim for 90–100g per hour by week 8, and test 110–120g per hour on at least two long rides in Phase 2. Use a mix of glucose and fructose in a 1:0.8 ratio to exceed the 60g glucose-only absorption ceiling. Sports drinks, gels, and rice cakes all work — brand matters less than consistency.
Hydration targets 500–750ml per hour, adjusted for heat. Sodium intake 500–1000mg per hour on long or hot rides. Caffeine 2–3mg per kg bodyweight, taken in the final 90 minutes of the bike for race-day run carryover.
Work out your exact hourly numbers using the in-ride fuelling calculator, then rehearse them on every long ride. Race day is not the day to try a new gel flavour or a new bottle mix.
The bike-to-run nutrition handoff matters as much as the bike itself. An Ironman run is fuelled 60% by what you ate on the bike. Arriving at T2 with depleted glycogen and a sloshing stomach is how four-hour marathons become six-hour walks. Keep fuelling in the final 30 minutes of the bike, even when it feels counterintuitive.
How to slot in swim and run without breaking the bike block
This is a bike-focused plan, but swim and run still happen. The trick is scheduling them so they support rather than sabotage the bike sessions.
Swim 2–3 times per week, 45–60 minutes per session. Technique work and threshold intervals. Total swim volume: 2–3 hours. Swim sessions carry minimal systemic fatigue cost when kept inside this range, so they can sit the morning of a hard bike session without compromise.
Run 3–4 times per week, total 3–5 hours. One long run (90–150 minutes) on Sunday or Monday. One tempo or threshold session midweek. One or two easy runs of 30–60 minutes. Plus 1–2 brick runs as already described.
The critical scheduling rule: never run hard the day before a key bike session, and never run long the day after one. Tuesday's sweet spot ride requires fresh legs. Saturday's long ride requires fresh legs. Protect those two sessions at the cost of any other.
A workable weekly skeleton: Monday rest or recovery swim. Tuesday AM bike key session, PM easy run. Wednesday swim plus tempo run. Thursday bike endurance or Zone 2. Friday swim plus easy run. Saturday long bike with optional brick. Sunday long run or Zone 2 bike with brick.
Most age-groupers who break this plan do so by adding an extra run session in Phase
