So you've signed up for your first Ironman 70.3. Maybe you clicked register on a whim, maybe it's been on your bucket list for years — either way, you're probably now staring at the confirmation email wondering what on earth comes next.
First, take a breath. The 70.3 — a 1.9km swim, 90km bike, and 21.1km run — is absolutely achievable for a first-timer. Thousands of people complete one every year with no prior triathlon experience. What separates those who cross the finish line feeling strong from those who struggle is one thing: a structured, intelligent training plan.
Here's everything you need to know to get from where you are now to that finish line.
How Much Time Do You Need?
Most first-timers need between 16 and 24 weeks of structured training, depending on your current fitness base. If you're already running regularly or cycling a few times a week, 16–20 weeks is realistic. If you're starting from scratch across all three disciplines, give yourself closer to 24 weeks.
Don't panic if your race is sooner than that. A good coach can work with what you have. What matters is that you don't cram — consistency over time beats heroic training blocks every time.
Building Your Base: The First 8 Weeks
The biggest mistake first-time 70.3 athletes make is going too hard, too soon. The first phase of your training should feel almost boring — and that's exactly right.
Your focus in these early weeks is aerobic base building. This means:
- Swimming 2–3 times per week, prioritising technique over distance. Poor swim technique will cost you energy you need on the bike and run. If you can, get a swim coach or join a masters swim group early in your training.
- Cycling 3 times per week, keeping effort low and building time in the saddle. Long weekend rides at a conversational pace are your best friend.
- Running 3 times per week, again at easy effort. If you can't hold a conversation while running, you're going too fast.
Total training volume at this stage might be 8–10 hours per week. That's enough. Resist the urge to do more.
Building Specific Fitness: Weeks 8–16
Once you have a solid base, you can start adding intensity and specificity. This is where training starts to feel genuinely race-focused.
Swim: Begin working on open water confidence if you haven't already. Pool swimming and open water feel very different — sighting, wetsuit swimming, and mass starts are all skills that need practice. Aim to get into open water at least once a fortnight from this point.
Bike: Your long ride should be building towards 4–5 hours comfortably by the end of this block. Start practising your race nutrition on the bike — gels, bars, and hydration that you'll use on race day. Never try anything new in a race.
Run: Introduce brick sessions — runs done immediately off the bike. These train your legs to adapt to the shift from cycling to running muscles, and nothing quite prepares you for that jelly-leg feeling like doing it repeatedly in training. Start with 20–30 minutes off the bike and build from there.
Intensity work — threshold intervals, tempo runs, harder bike efforts — should make up no more than 20% of your total training volume. Most of your time should still be at easy, aerobic effort.
Understanding Training Zones
You'll hear a lot about training zones — and for good reason. Training at the right intensity on the right day is what makes a training plan work.
At its simplest:
- Zone 2 (easy/aerobic): Where most of your training happens. Builds your aerobic engine without accumulating fatigue.
- Zone 3–4 (threshold): Hard but controlled. Used sparingly in interval sessions.
- Zone 5 (VO2 max): Very hard, short efforts. Used even more sparingly.
If you want a precise picture of your zones, lactate testing is the gold standard. Rather than estimating from generic formulas, a lactate test identifies your exact physiological thresholds across heart rate, pace, and power — so every training session is targeted with precision. It's one of the most valuable investments you can make early in your training.
The Taper: Your Final 1–2 Weeks
One to two weeks out from race day, you begin tapering — deliberately reducing training volume while maintaining some intensity. This allows your body to absorb all the fitness you've built and arrive at the start line fresh.
Tapering can feel uncomfortable. You'll feel like you're losing fitness, getting slow, maybe even coming down with something. You're not. Trust the process.
In your final week, keep sessions short and sharp. Get your kit ready early, sort your race-day nutrition, and do a course recce if you can. Arrive at race day rested, not exhausted.
What to Do on Race Day
Pace the swim conservatively. The adrenaline will make you want to sprint — resist it. Find open water, settle into your stroke, and get through transition calmly.
On the bike, the temptation is to ride too hard early. Stick to your plan. A common rule of thumb: if you think you're going too easy in the first half of the bike, you're probably going just right. Your goal is to arrive at T2 with legs still in them.
The run is where the race is won or lost. Start slower than you think you need to, nail your nutrition, and build through the second half. When you hit the finishing chute — and you will — take it all in.
Do You Need a Coach?
Technically, no. Plenty of people complete a 70.3 off a generic training plan downloaded from the internet. But those who work with an experienced triathlon coach consistently report better race performances, fewer injuries, and — perhaps most importantly — a training experience they actually enjoy rather than just survive.
A coach adapts your plan to your life, your fitness, and your specific weaknesses. They take the guesswork out of every session and keep you accountable when motivation dips — which it will.
If you're serious about not just finishing but finishing well, coached training is the single biggest upgrade you can make.
Ready to take on your first 70.3 with a plan built around you? Get in touch with the Optimal Endurance Coaching team and let's build something together.
Coach Ross