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Triathlon · 20 weeks20-week 70.3 half Ironman training plan
A 20-week 70.3 half Ironman training plan takes a club triathlete with a 55-minute 10 km, an FTP of 220 W and a 7:30 400 m swim from where they are to race day in 21 weeks, building to 19h20 of training in the biggest week. It spends 9 weeks in base, 8 weeks in build, 2 weeks in peak, 1 week in taper, with 4 lighter weeks to absorb the work, on 6 days a week.
Build my 70.3 half Ironman plan — freeBuilt from your own numbers and your own week. The first week is free.
20 weeks is a comfortable length for a 70.3 half Ironman. There is room for a proper base before the harder work, lighter weeks to absorb it, and a taper that leaves you fresh rather than flat.
The 70.3 half Ironman is a 1.9 km swim, a 90 km ride and a 21.1 km run, and the plan manages all three as one load — two sports that each look reasonable on their own are the commonest way triathletes dig a hole.
What the weeks are for
| Base | 9 weeks — aerobic volume, mostly easy, the foundation everything else stands on |
|---|---|
| Build | 8 weeks — the harder sessions arrive and volume keeps climbing |
| Peak | 2 weeks — the biggest, most race-specific weeks |
| Taper | 1 week — volume drops, intensity stays, you arrive fresh |
| Lighter weeks | 4, roughly every fourth week |
| Total | 311 hours |
The 21 weeks
Generated for a club triathlete with a 55-minute 10 km, an FTP of 220 W and a 7:30 400 m swim.
| Week | Phase | Volume | Load | |
|---|---|---|---|---|
| 1 | Base | 30 km | 515 | |
| 2 | Base | 33 km | 551 | |
| 3 | Base | 36 km | 590 | |
| 4 | Base · down | 24 km | 363 | |
| 5 | Base | 39 km | 637 | |
| 6 | Base | 41 km | 670 | |
| 7 | Base | 44 km | 701 | |
| 8 | Base · down | 30 km | 441 | |
| 9 | Base | 47 km | 730 | |
| 10 | Build | 50 km | 803 | |
| 11 | Build | 53 km | 851 | |
| 12 | Build · down | 36 km | 558 | |
| 13 | Build | 56 km | 881 | |
| 14 | Build | 53 km | 892 | |
| 15 | Build | 56 km | 919 | |
| 16 | Build · down | 42 km | 650 | |
| 17 | Build | 59 km | 947 | |
| 18 | Peak | 62 km | 970 | |
| 19 | Peak | 65 km | 994 | |
| 20 | Taper | 42 km | 621 | |
| 21 | Race · race | 26 km | 291 |
The biggest week, session by session
Week 19, peak phase — the heaviest week of the block.
| Monday | Easy run — 0h57, 7.6 km |
|---|---|
| Monday | Endurance ride — 1h12 |
| Monday | Technique and drills — 0h35, 2 km |
| Tuesday | Threshold — 2 × 10 min — 0h54, 7.6 km |
| Tuesday | Strength — lower body — 0h27 |
| Tuesday | VO₂max — 5 × 4 min — 1h06 |
| Tuesday | Open water — 1h13, 3.4 km |
| Wednesday | Easy run — 0h57, 7.6 km |
| Wednesday | Endurance ride — 1h12 |
| Friday | Race pace — 8 km — 1h09, 10.2 km |
| Friday | Sweet spot — 3 × 15 min — 1h10 |
| Saturday | Easy run — 0h57, 7.6 km |
| Saturday | Long ride with race efforts, then run — 3h00 |
| Sunday | Long run with a fast finish — 2h42, 24 km |
| Sunday | Endurance ride — 1h12 |
| Sunday | Speed — 8 × 100 m — 0h37, 1.8 km |
Paces, power and swim speed
| Pace band | Per kilometre |
|---|---|
| Easy — the ceiling, not the target | 6:40 |
| Marathon pace | 6:00 |
| Threshold | 5:40 |
| Interval (VO₂max) | 5:08 |
Computed from VDOT 35.8, derived from that time trial using Jack Daniels' model. Your own numbers will differ — the plan builds these from a time trial you enter.
On the bike
| Recovery | 0–121 W — Easy enough to be slightly boring. That is the point. |
|---|---|
| Endurance | 123–165 W — All-day pace. Conversational, and most of your riding. |
| Tempo | 167–191 W — Working, but you could hold it for an hour or more. |
| Sweet spot | 194–207 W — Most of the threshold benefit for much less fatigue. The workhorse. |
| Threshold | 209–231 W — About what you could hold for an hour, flat out. |
| VO₂max | 233–264 W — Three to five minutes at a time and no more. Deeply unpleasant. |
Andrew Coggan's zones as fractions of an FTP of 220 W. No power meter? The plan prescribes the same sessions by heart rate off your threshold heart rate instead.
In the water
| Critical Swim Speed | 1:59 per 100 m |
|---|---|
| Recovery | 2:09/100 m — Easy enough to think about your stroke rather than your lungs. |
| Endurance | 2:04/100 m — Steady. You could keep going for a long time. |
| CSS | 1:59/100 m — Threshold. Hard but repeatable across a whole set. |
| VO₂max | 1:56/100 m — Faster than threshold, in short reps with real rest. |
| Speed | 1:53/100 m — Short and quick. Technique first, effort second. |
From a 400 m in 7:30 and a 200 m in 3:32, using the two-trial protocol (Wakayoshi et al., 1992). Your own CSS comes from your own two swims.
What this plan says out loud
Worth saying plainly about swimming: for most amateur swimmers, improvement comes from technique rather than fitness. This plan can prescribe the work. It cannot see that your hips are sinking or your catch is dropping, and no amount of threshold sets fixes a stroke. If you can afford one thing, buy a few sessions with a coach on the pool deck rather than more sets from us.
Some sessions have been cut to fit the time you said you have — 75 minutes on a weekday and 180 at the weekend. That is a real constraint and the plan respects it, but be aware the long session is the one that matters most: if you can find more time anywhere, find it on the weekend.
On 6 days a week there is nowhere to put 28 km without prescribing runs nobody should be doing. The plan caps individual easy runs at 14 km and carries less volume than your target as a result. More days would do more for you than longer runs.
Common questions
Is 20 weeks enough for a 70.3 half Ironman?
Yes, for most people who already exercise. We would choose at least 16 weeks, and this is 20.
How many days a week does it train?
6, on Monday, Tuesday, Wednesday, Friday, Saturday, Sunday in this example. You tell the plan which days you actually have, and it never puts two hard days back to back.
What is the longest session?
Long ride, about 3h00. It is capped by share of the week, by absolute length, and by the time you say you have.
Can I use this if I train at altitude?
Yes, and you should say so when you build it. Paces and power are corrected for the difference between where you tested and where you train — in Johannesburg that is roughly 8%, or about 26 seconds a kilometre on an easy run for a 20-minute 5 km runner.