Ironman Training Plan: A 24-Week Roadmap for Your First (or Fastest) 140.6
What 24 weeks of Ironman training actually looks like — phases, weekly hours, key sessions, and the brick workouts that separate finishers from sufferers.
An Ironman isn't a longer triathlon — it's a different sport. The same athlete who can wing a half-ironman off six weeks of focused training will get destroyed by 140.6 if they try the same. This guide breaks the full 24-week build into the four phases that actually work, with weekly hours and key sessions for each.
Phase 1 — Base (weeks 1–8)
Goal: aerobic foundation, swim consistency, durability. Weekly hours 8–12. All three sports moved at low intensity (Z1–Z2). Two swims, three rides, three runs, one strength session. The longest sessions of the phase: a 2.5-hour ride and a 90-minute run by week 8. No racing, no testing, no heroics.
Phase 2 — Build (weeks 9–16)
Goal: introduce race-pace intensity, extend duration. Weekly hours 11–15. Key sessions arrive: 4×8' bike threshold intervals, 5×1mi run T pace, race-pace swim sets. Long sessions grow: 4-hour ride, 2-hour run, weekly brick. By week 16: 5-hour ride, 2:15 run.
Phase 3 — Specific (weeks 17–22)
Goal: race-rehearsal — execute the day. Weekly hours 13–17 (peak). The biggest weeks of the cycle: a 6-hour ride paired with a 30' run brick, a 3-hour run, two race-pace bricks. Fueling becomes a workout — practice 60–90g/hr carbs on every long session.
Phase 4 — Taper (weeks 23–24)
Goal: arrive fresh, sharp, and confident. Weekly hours drop to 60% then 40% of peak. Keep intensity, slash duration. Final two weeks: short race-pace efforts in all three sports, full nutrition rehearsal, gear check, drive the course if local.
Key weekly sessions throughout
The long ride + brick
Saturday tradition: ride 3–6 hours steady aerobic, then run 15–30 minutes off the bike at goal Ironman pace. This is the most important session of the week — physically and mentally. It's where you learn to fuel, pace, and run on legs that feel like concrete.
The long run
Sunday, after the brick day. 90 minutes to 3 hours, all aerobic, fueled aggressively (60g/hr carbs minimum). The goal isn't speed — it's time on feet without breakdown.
The threshold session
Once per week per sport: 3×10' bike at FTP, 5×1mi run at T, 8×100m swim race-pace. Maintains the top-end you need to clear the swim cutoff and bike strong.
An Ironman is won and lost on the bike. Pace the bike like a coward, and you'll run like a champion.
Nutrition rules that don't change
- Bike: 60–90g carbs per hour, 500–750ml fluid per hour, 500–1000mg sodium per hour
- Run: drop to 45–60g carbs (gut tolerance), cola from mile 10 onward is a coach's secret
- Practice exact race-day fueling on every long session — never try anything new on race day
- Pre-race breakfast: 3 hours out, 100–150g carbs, low fiber, low fat
Common 24-week mistakes
- 01Skipping bricks because they're tedious — they're the most race-specific session you do
- 02Racing or hammering a half-ironman 4 weeks out (too close to peak; recovery costs too much)
- 03Tapering too short — 10 days is not enough for 140.6
- 04Underestimating heat — train in it if your race is in heat, or cap your goal accordingly
Questions athletes ask about this
- Can I do an Ironman with less than 24 weeks of training?
- Yes, if you already have a 10-12 hour weekly base. From zero, 24 weeks is the minimum that produces a confident, well-fueled performance rather than a survival shuffle.
- How many hours per week peak for first Ironman?
- 12–17 hours during the specific phase. Beyond 17, fatigue costs typically outweigh fitness gains for amateur athletes.
- Do I need a coach for my first Ironman?
- Not strictly, but a coach pays for themselves in race-day execution alone. Most DIY first-timers blow up the bike pace and run-walk a marathon they could have run.
- What's the longest ride I should do before the race?
- 5–6 hours, usually 6–8 weeks out. Don't simulate the full bike split — the marginal aerobic gain isn't worth the recovery cost.
- Should my long run be 26.2 miles?
- No. Cap long runs at 2:30–3:00 hours. The combined load of the bike block makes a stand-alone marathon-distance run more costly than helpful.
Want this kind of thinking applied to your training?
Free 20-minute call. We'll talk about your race, your timeline, and whether 1:1 coaching is the right next step.
Book a discovery callEndurance coach since 2015. RRCA-certified, USAT Level II, TrainingPeaks Level 2. 12× Boston Marathon qualifier. Based in Fenway, Boston — coaching athletes worldwide in English, Portuguese, and Spanish.
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