Ironman Training Plan: 20-Week Guide to Your First 140.6

The Ironman Challenge

An Ironman is 3.8km swim, 180km bike, and a full 42.2km marathon — back to back, with a 17-hour cutoff. It’s the hardest single-day endurance event most athletes will ever attempt.

You don’t need to be fast. You need to be prepared. This 20-week plan is designed for intermediate athletes who can already swim 1500m, ride 2 hours, and run 10km. If you can’t do those yet, spend 8–12 weeks building to those baselines first.

Plan Overview

Periodization Structure

Phase	Weeks	Focus	Weekly Hours
Base	1–8	Aerobic foundation, technique	8–12h
Build	9–14	Race-specific intensity	12–16h
Peak	15–17	Longest sessions, race simulation	14–18h
Taper	18–20	Volume reduction, sharpening	6–10h

Weekly Session Distribution

Swim: 3 sessions (15–20% of volume)
Bike: 3 sessions (45–55% of volume)
Run: 2–3 sessions (25–30% of volume)
Brick: 1 per week in Build/Peak phases
Strength: 1–2 in Base phase, drop in Peak

Phase-by-Phase Guide

Base Phase (Weeks 1–8)

Goal: Build aerobic engine, lock in technique, establish training routine.

The base phase is about consistency, not intensity. Swim technique matters more than swim fitness — a 10% improvement in stroke efficiency saves more energy than a 10% improvement in swim fitness.

Key sessions:

Long ride: Building from 2h to 4h at conversational pace. Practice nutrition every 30 minutes.
Long run: Building from 60 to 90 minutes. Easy pace — you should be able to talk in full sentences.
Swim technique: 2×/week focusing on catch, body rotation, and bilateral breathing. Include drills (catch-up, fingertip drag, fist drill).
Strength: 2×/week. Focus on core stability, single-leg work, and shoulder health.

Weekly volume progression:

Weeks 1–2: 8–9h
Weeks 3–4: 9–10h
Weeks 5–6: 10–11h
Weeks 7–8: 11–12h (with a recovery week at week 4 and 8)

Build Phase (Weeks 9–14)

Goal: Introduce race-specific intensity. Learn to fuel. Practice pacing.

This is where training gets real. You’ll add tempo efforts, hill work, and — critically — brick workouts.

Key sessions:

Brick workout (Saturday): Tempo bike (60–90 min) immediately followed by a 30–45 min run at race pace. This trains your body for the bike-to-run transition.
Threshold swim: 5×200m at threshold pace with 20s rest. Build swim endurance and speed.
Tempo ride: 60–90 min at race effort. Practice aero position and nutrition.
Long run with race-pace segments: 90–120 min with 20–30 min at target marathon pace in the middle.

Weekly volume progression:

Weeks 9–10: 12–13h
Weeks 11–12: 13–15h
Weeks 13–14: 14–16h

Peak Phase (Weeks 15–17)

Goal: Longest sessions. Race simulation. Confidence building.

Peak phase includes your longest training sessions. Week 16 or 17 typically includes a “race rehearsal” — a 5–6 hour session combining a long ride with a medium run.

Key sessions:

Race simulation (weekend): 4–5h bike + 45–60 min run. Practice race nutrition, pacing, and mental strategy.
Long swim: Build to 3000–3500m continuous. Practice open water sighting.
Long ride: One ride of 5–6 hours at race effort.

Volume: 14–18h per week. This is the hardest phase physically and mentally. Trust the plan and prioritize sleep.

Taper Phase (Weeks 18–20)

Goal: Reduce volume 40–60% while keeping intensity. Arrive fresh.

Week 18: 70% of peak volume. Keep one race-pace session per discipline. Week 19: 50% of peak volume. Short, sharp efforts only. Week 20 (race week): 30% volume. Easy swims, short spins, 20-min shakeout runs. Practice transitions. Rest.

Taper anxiety is normal. You’ll feel sluggish, doubt your fitness, and want to do one more long ride. Don’t. The fitness is banked. Let your body absorb it.

Key Ironman Training Principles

1. The Bike Determines the Run

Your marathon time is determined on the bike. Push too hard on the bike and you’ll walk the marathon. Train to ride at a sustainable effort — typically 70–75% of your FTP or an effort where you can still speak in short sentences.

2. Nutrition Is the Fourth Discipline

Practice eating on every long ride. Aim for 60–90g carbs per hour. Test gels, bars, and drinks in training — never on race day.

3. Consistency Beats Heroics

Missing one workout doesn’t matter. Missing a week of sleep does. Prioritize recovery: 7–9 hours of sleep, easy days that are actually easy, and a recovery week every 3–4 weeks (reduce volume by 30–40%).

4. Open Water Swimming Is a Skill

Pool fitness doesn’t equal open water competence. Practice sighting, drafting, mass starts, and swimming without walls at least once a week during Build and Peak phases.

5. Heat Adaptation Matters

If your race is hot (>25°C), spend the final 10–14 days doing some training in heat. Sauna protocols also work: 20–30 min post-workout, 4–5 times in the final 2 weeks.

Race-Day Quick Reference

Pre-race meal: 2–3h before. 600–800 calories. Familiar foods.
Swim: Start easy. Sight every 6–8 strokes. Draft if possible.
T1: Wetsuit off, helmet on, eat a gel, go.
Bike: Easy first 30 min. Settle into race pace. Eat every 20 min. Drink to thirst.
T2: Rack bike, helmet off, run shoes on. Walk T2 — it saves energy for the run.
Run: Walk the first aid station. Run easy for 3km until your legs adjust. Then settle into pace.
Mile 20+: This is where Ironman happens. Slow down if needed. Walk aid stations. Take in calories. Keep moving.

Generate your personalized plan on our Training Plan page — we’ll tailor the schedule to your specific race course, weather conditions, and goal time.