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 — particularly Asker Jeukendrup's work on CHO oxidation and multiple transportable carbohydrates — 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 2 or pushing the long ride past six hours. Both feel virtuous. Both wreck the marathon.
What breaks this plan
Five mistakes account for almost every blown 16-week build. Every one is fixable, and none of them are about lacking the engine.
Riding the long ride too hard. Phase 1 long rides sit at 65–70% of FTP. Phase 2 long rides include race-pace blocks but the bulk of the time is still aerobic. If your average power on a five-hour ride is 75% of FTP, you are not building Ironman fitness — you are building tired. The ride has to feel boring through the middle to be useful at the end.
Skipping recovery weeks. Weeks 4, 10, and 13 are not optional. The athletes who treat them as "I feel good, I'll keep going" weeks are the ones who arrive at weeks 11–12 cooked and miss the biggest sessions of the plan. Volume drops 30–40%. Intensity holds. Adaptation happens in the gap.
Fuelling on race day what you never fuelled in training. If you have not absorbed 100g of carbohydrate per hour on a five-hour ride in Phase 2, do not try it on race day. The gut trains the same way the legs do — slowly, repeatedly, and mostly invisibly. Race day rewards what you rehearsed.
Stacking extra run volume in Phase 2 or 3. When the bike sessions start to bite, the instinct is to "balance" the week with more running. It backfires every time. Phase 2 is the most expensive phase of the plan in terms of recovery cost. Run only what's prescribed. The marathon is built on the bike, not on extra weekly mileage.
Testing fitness in taper. Week 14 and week 15 are not the place to chase a Strava KOM or "see where the FTP sits now." That work is already done. The taper isn't checking whether the fitness is there — it's letting it surface. One ego ride in week 15 can erase the freshness of the whole final block.
If you find yourself drifting toward any of these, that's the moment to rein in, not push on. The plan only works if you let it work.
Pacing the bike on race day
The taper sessions in Phase 3 cover your race week. Race day itself is a pacing exercise dressed up as a power test. Most age-groupers race their Ironman bike at 65–72% of FTP. Stronger runners who want to protect the marathon ride closer to 65%. Athletes with weaker run history or limited race experience stay under 70%. Anything above 75% almost always costs more on the run than it saves on the bike.
Split the 180km into three blocks and the pacing takes care of itself.
0–60km. Cap power 10–15 watts below your goal. Heart rate is still elevated from the swim and the watts will feel laughably easy. They are not. Every age-grouper who blows their Ironman bike does it in the first 90 minutes. Sit on your hands and ride steady.
60–140km. Settle into goal power. Fuel every 15 minutes by the clock — a feed you have to set a timer for is a feed you actually take. 90–110g of carbohydrate per hour through this block, 600–800ml of fluid, sodium dialled to conditions. Stay aero. The biggest free time on the course is in the position you hold, not the watts you push.
140–180km. This is where the race is decided. Hold power, not perceived effort. RPE drifts up while watts drift down, and that gap is what costs you the marathon. Keep fuelling to T2 — the final 30 minutes of the bike still feeds the first 90 minutes of the run.
Ease the final two kilometres into transition. You lose 20 seconds on the bike split and gain two minutes in the opening 5km of the run. It is not a close trade.
If you don't have a power meter, the same plan still works — heart rate and perceived exertion become the primary tools. Zone 2 is conversational pace, roughly 70–80% of max heart rate. Sweet spot feels like a hard tempo you could sustain for 30–40 minutes if you had to. Race-day pacing without a power meter relies more on discipline than on numbers, which means the first 60km matters even more. Add a power meter inside the 16 weeks if you can — it is the single best equipment upgrade you can make for an Ironman.
Pulling it together
A 16-week Ironman bike build does not need to be complicated. It needs to be honest.
Honest about the FTP you actually have. Honest about the hours you can actually train without breaking sleep, work, or the people you live with. Honest about the fact that the bike leg of an Ironman is a pacing and fuelling exercise dressed up as a 180km time trial. The age-groupers who execute this plan well are not the strongest. They are the ones who believe the framing — that the bike exists to protect the run — and ride accordingly for sixteen weeks straight.
Test FTP in week one. Map the weekly skeleton to the rhythm above. Pin the recovery weeks in your calendar in red so you can't talk yourself out of them. Practise fuelling from the first long ride, not the fifth. Train your race position from week one, not week ten.
If you want the plan adjusted to your FTP, your race course, and your run history, that is what we do inside Not Done Yet. Sixteen weeks of self-execution from this template will get most age-groupers to the line ready to race. Sixteen weeks with the plan adjusted weekly to what your power files, your sleep, and your brick runs are actually saying will get you there ready to race well.