An Ironman is a 3.8km swim, 180km bike, and 42.2km run completed in a single day. For most athletes, it takes 10–17 hours. The training to get there takes 30 weeks, 12–20 hours per week, and a level of life organization that goes well beyond buying a training plan. This guide covers the full structure — what the periodization looks like, how the long ride and long run fit together, how to pace the bike for a 42km run that follows, and how to eat for 10+ hours of sustained effort.
What You Are Actually Signing Up For
The gap between a 70.3 and a full Ironman is larger than the doubled distances suggest. The bike leg is 180km — typically 5–7 hours for age-groupers. The run is a full marathon that begins after those 5–7 hours of riding. Peak training weeks reach 15–20 hours. The long ride alone is 5–6 hours, the long run 2h30–3h. These sessions consume entire days and require meticulous recovery management.
That said, thousands of athletes finish an Ironman every year while holding full-time jobs. The key is not total hours but intelligent periodization: making every session count and never digging a hole you cannot recover from before the next key session.
The 30-Week Periodization Structure
A 30-week plan divides into four blocks:
- Base (weeks 1–10): Aerobic volume. Mostly zone 1–2. TSS builds from 350 to 550. Swim technique focus, cycling endurance, run frequency.
- Build (weeks 11–22): Race-specific intensity introduced. Threshold intervals, long brick sessions. TSS reaches 700–900. The fitness that actually gets you to the finish line is built here.
- Peak (weeks 23–26): Highest training load. Two race-simulation weekends. TSS hits 900–1,100 in the biggest weeks. Volume and intensity peak simultaneously — manage recovery carefully.
- Taper (weeks 27–30): Volume drops 50–60%, race-pace intensity maintained. Final 10 days: mostly easy with short race-effort intervals. Arrive fresh.
Track your CTL progression with the Training Load Calculator. A target CTL of 90–120 by week 24 puts you in position for a solid finish.
The Long Ride and Long Run
These are the two sessions that define your Ironman preparation. The long ride peaks at 5–6 hours in week 22–24. Ride it at zone 2 (65–75% FTP) — anything harder destroys recovery and teaches your body to burn carbohydrate at a rate that is unsustainable for 7 hours of racing. The last 45–60 minutes at 80–85% FTP simulates the race-day fade and teaches you to keep pushing when tired.
The long run peaks at 2h30–3h — never the full 42km. Running a training marathon risks injury and rarely improves race performance. Your longest run builds the structural durability needed to complete the marathon after 7+ hours of prior effort. Keep it at 65–70% of max HR throughout.
Use the Recovery Readiness Calculator to manage the recovery load these sessions generate.
Race-Day Pacing: The Bike Leg
Ironman bike pacing is the most consequential decision of your race. Going 5% too hard on the bike costs you 20–40 minutes on the run. The target: 70–75% of FTP for the 180km. For an athlete with a 280W FTP, that is 196–210W average power. It feels embarrassingly easy for the first 60km. Ride it anyway.
Variable terrain demands variable power: ride 5–8% over target on climbs, let it drop 5% on descents. Aero position matters — every minute you spend upright is wasted. Use the FTP/VDOT Estimator to confirm your current FTP before setting power targets.
Ironman Nutrition: Fueling for 10+ Hours
Ironman nutrition is genuinely complex. You will consume 2,500–4,000 kcal during the race. The stomach becomes progressively harder to use as the day goes on and core temperature rises. Early fuel management determines late-race capacity.
Bike protocol: 80–100g carbohydrate per hour, starting at 20 minutes. Use real food (banana halves, rice cakes, or the race's specific gels) in the first 3 hours when your gut is fresh. Shift to liquid carbohydrate sources later. Sodium: 800–1,200mg/hr in hot conditions.
Run protocol: 40–60g carbohydrate per hour via aid station cola, gels, and broth. Broth provides sodium and is easier to digest than sweet foods late in the race. Coke has been a marathon staple for 50 years — the caffeine and simple sugar are genuinely useful after hour 9.
The TDEE Macro Planner calculates your training day calorie requirements to support 15+ hour training weeks.
Periodizing Around Work and Life
Ironman training with a full-time job is a scheduling problem as much as a fitness problem. The 30-week plan requires 12–20 hours per week — a schedule most people can fit in with careful design but not by accident.
Core structure: two weekday quality sessions (intervals), two weekday easy sessions (active recovery), long ride on Saturday, long run on Sunday. One swim each day that has a swim facility. Total: 8–10 sessions per week. The two quality sessions are non-negotiable; the easy sessions can shift to meet life demands.
Critical constraint: the long ride and long run form a weekend block. Miss these and you miss the primary fitness stimulus of the week. Build the rest of your life around Saturday and Sunday mornings, not the other way around.
How Adaptive AI Training Changes the Game
Ironman training spans 30 weeks — long enough that illness, work travel, injury, and unexpected life events are not edge cases, they are certainties. A static plan treats week 14 as if nothing happened in weeks 1–13. An adaptive system updates in real time.
When your HRV crashes after a hard week, the AI reduces load for 3–5 days and rebalances the following week's structure. When you miss a 5-hour ride due to travel, it calculates what was actually lost and adjusts the build trajectory. When you add a new FTP test result, every future power target updates automatically. The result is a periodization plan that bends to reality instead of breaking against it.
An Ironman is the longest standard triathlon distance and one of the most demanding single-day endurance events in amateur sport. The 30-week framework above gives you the periodization architecture. Use the prompt builder below to generate a personalized training week that accounts for your current fitness, available hours, and where you are in the build.