IRONMAN 70.3 Training Plan: 20 Weeks to Your First Half IRONMAN (Coach's Method)
"I can find a free plan online, so why would I need a coach?"
Fair question. Here's my honest answer: a generic plan can get you to the finish line of a 70.3. What it won't know is that you had a brutal week at work, that your knee started complaining on Sunday's long ride, or that you went out way too fast on your swim test.
A plan is only as good as its fit with you: your fitness right now, your schedule, your life. That's what this article is about. How I actually build a 70.3 preparation for age-groupers with jobs and families, based on what the science says today.
A bit of background: I'm an IRONMAN Certified Coach based in France. I've raced the full distance in 9:17 and the 70.3 in 4:15, and I've helped more than 125 athletes get to the finish line, 70 of them at the 70.3 or full distance.
IRONMAN 70.3: what race day really feels like
Before we talk training, you need to know what your body is going to go through.
The numbers:
Swim: 1.2 miles (1.9 km) in open water, mass or rolling start
Bike: 56 miles (90 km), usually with 650 to 3,300 ft of climbing depending on the course
Run: 13.1 miles (21.1 km), a half marathon on tired legs
Cut-off: 8 hours 30 minutes
Typical age-group finish: somewhere between 5:30 and 7:00
What most people don't realize before their first one:
The swim isn't the hardest part physically, but it's the most stressful. Open-water start, elbows everywhere, no black line to follow... If you haven't practiced it, your heart rate shoots up and you climb out of the water drained before you've even touched your bike.
The bike is by far the longest part. Most people spend 2:30 to 3:30 in the saddle, and that's where your finish time is made or lost.
The run shows up when you're already tired. The hard part isn't running fast. It's running at all on quads that 56 miles of riding have already chewed up.
The three kinds of athletes I see training for a 70.3
Before you build a plan, you have to know who it's for. In my coaching, people taking on a 70.3 usually fall into one of three groups.
The first-timer. Usually comes from running or cycling, swims a little (or badly), and wants to finish. Upright, within the cut-off, without getting hurt. They need 20 to 24 weeks, with a lot of attention on swim technique and pacing on the bike.
The experienced racer. Has done one or more 70.3s and wants a PR. What holds them back is usually very specific: too fast in the swim, not enough power on the bike, or a blow-up in the last 4 miles of the run. They need 16 to 20 weeks of targeted work and regular testing.
The time-crunched athlete. A manager, a parent, often both. Can't train more than 8 to 10 hours a week. Every hour has to count, so there's no room for junk miles in the plan.
How I structure a 20-week IRONMAN 70.3 training plan
Here's how I'd lay out a typical build for an intermediate athlete with 10 to 12 hours a week.
Phase 1: aerobic base (weeks 1 to 6)
Goal: build the foundation without getting injured.
About 80% of the sessions are easy, below your aerobic threshold. That's where your body learns to burn fat efficiently and to handle volume without piling up fatigue.
A typical week:
Swim: 3 sessions, 4.5 to 5.5 miles total (7 to 9 km)
Bike: 3 rides, 5 to 6 hours total, including one long weekend ride
Run: 3 runs, 19 to 25 miles total
Strength: 2 x 30 min (core, eccentric lower-body work)
Key session: the Sunday long ride. Start around 2 to 2:30 and build up to 3:30 or 4 hours by the end of the phase. Easy effort, legs spinning. Boring? Yes. Essential? Absolutely.
In the pool, it's all about body position. If your legs sink, you're basically dragging a parachute. For the first few weeks my athletes work on technique only, not distance. 2,000 yards swum well beat 4,000 swum badly.
Phase 2: build and threshold (weeks 7 to 14)
Goal: more power, more resistance to fatigue.
This is the heart of the plan. Threshold work comes in (zone 4 on a 5-zone scale), bricks become a weekly habit, and the long rides hit their peak.
A typical week:
Swim: 3 sessions, 5.5 to 7.5 miles total (9 to 12 km)
Bike: 3 rides, 6 to 8 hours total, including a 4 to 4:30 long ride
Run: 3 runs, 25 to 34 miles total
Bricks: 1 or 2 a week (30 to 45 min bike + 20 to 30 min run)
Bike: threshold intervals on the trainer or the road. For example 3 x 15 min at 95 to 100% of FTP, 5 min easy between. They hurt a bit, and that's the point.
Run: progressive tempo runs, like 9 miles with the last 5 at goal half-marathon pace. They teach you to hold pace when the tank is getting low.
Bricks: off the bike and straight into a run, no break. For the first 10 minutes your legs feel like wood. You want to know that feeling very well before race day.
Watch out: this is when injuries show up if the load climbs too fast. I stick to a simple rule, 3 weeks of loading and then 1 lighter week. Lighter doesn't mean off. It means 20 to 30% less volume, with a bit of intensity kept in.
Phase 3: race specificity (weeks 15 to 18)
Goal: train the way you'll race.
Now most of the quality work is done at your target 70.3 effort. Sessions get shorter but more precise, with full or partial race simulations.
The big one: the mock race day. Around week 16 or 17 I schedule a simulation. 1,500 m open-water swim, 37 miles on the bike at race effort, then 6 miles at race pace. It's a long and very revealing day, because it shows you exactly where the weak spots are before race day does.
It's also when you test your race nutrition for real. Which gels, which drink, how much at each aid station. Nothing should be new on race morning.
Phase 4: taper (weeks 19 and 20)
Goal: show up fresh, confident and ready to go.
The taper is the most misunderstood part of the plan. A lot of athletes are scared of losing fitness, so they keep training hard for too long.
What actually happens is this: your body needs 7 to 21 days of reduced load to supercompensate, and that's when fitness peaks. Train hard in that window and you waste the peak.
Week 19: cut total volume by 30 to 40%. Keep a few short race-effort blocks (15 to 20 min on the bike and the run) so you don't lose the feel. Sleep more, eat well.
Week 20 (race week): almost nothing. A short swim Tuesday, an easy spin Wednesday, a 20 to 25 min run Thursday with a few strides, rest Friday, a short ride on the course Saturday if you can, race Sunday.
Sample Phase 2 week (build week)
Day | Sport | Session | Duration |
|---|---|---|---|
Monday | Rest | Active recovery / stretching | - |
Tuesday | Swim | 3,000 m: warm-up + 5 x 400 m at CSS pace + cool-down | 1h |
Tuesday | Run | 45 min easy (zone 2) | 45 min |
Wednesday | Bike | Trainer: 75 min with 3 x 12 min at 95% of FTP | 1h15 |
Thursday | Swim | 2,500 m technique + open-water swim if possible | 50 min |
Thursday | Run | 1h easy + 4 x 6 min at 100% of critical speed | 1h |
Friday | Rest or mobility | Yoga, stretching, foam roller | - |
Saturday | Brick | 2h30 bike including 30 min at race effort + 20 min brick run | 3h |
Sunday | Long run | 1h30 to 1h45 in zone 2 | 1h45 |
Total: about 10 hours
70.3 nutrition: what to know before the start
A 70.3 takes 4 to 7 hours. You'll burn somewhere between 2,500 and 4,500 calories, and your body only stores about 1,500 to 2,000 calories of glycogen. So yes, you have to eat during the race.
What current guidelines recommend on race day:
Carbs: 60 to 90 g per hour on the bike and the run, depending on how well you've trained your gut
Fluids: 17 to 27 oz per hour depending on the heat
Sodium: 400 to 800 mg per hour to prevent hyponatremia and cramps
The rules I give every athlete:
Never try anything new on race day. If you haven't tested it in training, it has no place in your 70.3.
Start eating early on the bike, within the first 20 minutes, even if you're not hungry. Once you're running on empty it's too late to catch up.
Go easy on solids at the start of the run. Your gut is usually least happy in the first 6 miles of the half. Thick gels and bars can cause trouble there, so lean on sports drink in that window.
Why a generic plan won't cut it for your 70.3
A free plan you find online makes a lot of assumptions that may not fit you at all:
that you sleep 8 hours a night
that your work week is predictable
that you don't have an old injury or a muscle imbalance
that your weak discipline is the same as everyone else's
My online triathlon coaching starts with you. A detailed questionnaire, field tests, a look at your training history. Then the plan changes every week based on how you're actually responding, with daily feedback on every session you upload to TrainingPeaks.
There's finishing a 70.3, and there's finishing one having made the most of every hour you had to train. That difference is usually what coaching is.
Racing a 70.3 in Europe?
More and more Americans pick a European 70.3 as their goal race. It's a trip, a family vacation, and the entry is often cheaper than the big US races.
It does add two things to the plan. Bike logistics: flying with your bike or renting one, building it after the flight, and getting a short ride in before race day. Jet lag: landing 3 to 4 days early and putting your last key sessions before the flight, not after.
I plan for both when I coach athletes racing abroad, and with Race + Travel we also take care of flights, bike transport and a hotel close to transition.
Have a 70.3 on your radar?
First half IRONMAN or chasing a PR, the best place to start is a free 30-minute call.
We'll go over your goal, your schedule and where you're at right now. I'll tell you how I'd build your plan, and if you want to go ahead, we can start that same week. Just fill in the short form below and I'll get back to you.
FAQ: IRONMAN 70.3 training plan
How many hours a week do I need to train for an IRONMAN 70.3?
For a first-timer, 10 to 12 hours a week is a good target. If you've done a few and you're chasing a PR, 12 to 15 hours. With 8 well-structured hours a week you can still finish a 70.3, as long as every session has a purpose.
How many weeks does it take to prepare for a 70.3?
Ideally 20 to 24 weeks if it's your first long-distance triathlon, and 16 to 20 weeks if you're an experienced triathlete. 12 weeks is the bare minimum to do it safely, but at that point there isn't much room left to improve.
Can I do a 70.3 without ever having done a triathlon?
Yes, as long as you have a solid base in at least one of the three sports and you start early enough (24 weeks minimum in that case). Several of my athletes did their first 70.3 without ever having raced a triathlon before. I'd still recommend a sprint or Olympic race along the way to practice the swim start and the transitions.
How many swim sessions a week for a 70.3?
Ideally 3, including at least one in open water once it's warm enough. Weekly volume goes from about 4.5 to 7.5 miles (7 to 12 km) depending on the phase. Technique comes before volume, especially if you come from running or cycling.
Do I need strength training for a 70.3?
Yes, especially in the first 6 to 8 weeks. Core work, eccentric work for the hamstrings and calves (to protect your tendons), and some shoulder and back strength for the swim. Two 30-minute sessions a week are enough.
Do I need a triathlon bike for a 70.3?
No. A road bike is totally fine to train for and finish a 70.3. A tri bike with an aero position saves time, but it's a big investment and your body needs time to adapt to the position. For a first one, train on what you already have and upgrade later if you catch the bug.
How do I avoid falling apart on the run?
Don't overcook the bike. Your target power shouldn't go above 75 to 80% of your FTP. Riding 5 to 10% too hard in the first 20 miles can cost you 20 to 40 minutes on the half marathon. How you pace the bike is the biggest factor in how your run goes.
What's the difference between a free plan and a coach for a 70.3?
A free plan doesn't move. It doesn't adapt when you get sick, when work blows up, when something starts to hurt, or when you improve faster than expected. Coaching adjusts all the time. You also get testing, a race strategy, nutrition guidance and someone in your corner the whole way.
You deserve a plan built around your real life, not around an imaginary athlete.
Free 30-minute call, no commitment.