Great news: you've signed up for your first 70.3 (half Ironman). Or perhaps you're a seasoned, intermediate 70.3 triathlete. Now you've got 300 tabs open on your browser, you're not sure which formula to follow or how to start, and you're not necessarily ready to go down the coaching route.
In this article I'm going to build you the whole framework you need to get through your first 70.3. Even if you're a sub-5-hour finisher, you'll hopefully learn something.
A quick story first. We're going back to 2003 or 2004, over 20 years ago, to my first half Ironman, in Australia, where you swim out along a long pier. I'd certainly never gone over Olympic distance, and I took that methodology and thought process into the half Ironman. But I was in my early 20s and had no idea about the strength required for a 90 km bike ride. I'd lost so much time out of the sea to the fast Australians, on a road bike with clip-on tri bars, that I had to run my way back through the field in the sweltering heat of peak summer. I finished somewhere around 5:20 - I can't remember exactly. I wasn't coached at the time, and what I learned carried over into my next phase of training.
Twenty years later, as an endurance coach who has helped hundreds of athletes through 70.3s, and after tons of races myself over the last 15 years, I want to share what I know. This isn't a cookie-cutter, cut-and-paste plan that will work for everyone. You're the individual. So I'll give you some really good takeaways to help you structure your own 16 to 18 week journey. As a framework it's customisable to your situation, and once you have it you can jig sessions around - TrainingPeaks is great for moving sessions about.
The framework is three blocks, in an 18-week build:
- Block 1 - Foundation: about six weeks building aerobic efficiency (shorten this if you have less time)
- Block 2 - Build volume and controlled intensity: longer sessions and your first exposure to race-specific work
- Block 3 - Race specificity and preparation: the last five to six weeks, including your taper
1. Start With You, Not the Plan
We always begin with the end goal in mind. If you're a beginner, the first goal should be to finish and complete the race. Ultimately you want to do as well as you can, but some people just want to tick the box, and that's fantastic. A plan off the shelf is great, but then we need to mould it to you. That's where the breakdown comes in, and where a coach is really helpful.
How it fits into your life
Are you a 23-year-old who recovers really quickly, or do you have two or potentially three children? Most of my clients have an average of two kids, and that's when how training fits into your life becomes really important - along with your work and other commitments. You don't recover as well as you did when you were 23 or 25.
Your training age
Your training history is really important, and it's often overlooked. When you start a journey in triathlon, you've usually got a background in some sort of sport, but training age is measured in years. Have you been running or riding a bike, developing your aerobic foundation, for years? Or are you coming out of, say, football, with short bursts, or racket sports? Then you don't have a high training age.
That's true even if you come from a swimming background: you don't have the loading on your muscles, tendons and ligaments, and your joints tend to be quite lax. Those are things to consider, because when the running mileage starts to increase you can pick up problems, and unfortunately it normally comes quite late in the process, 8 to 12 weeks in, and by then you lose consistency.
Recovery, gender and injuries
I've done a separate video on the female triathlete, covering hormones, strength training and fasted training. Recovery is different between men and women, builds and strengths differ, and recovery times are an important consideration.
Are you also starting this process with an injury? It might be a shoulder or back niggle that prevents swimming, but 80% of the time it's running. A common way people fall into this is that they've been on a marathon plan for a long time, then a friend signs up for a 70.3 and they get excited - but they're running 50, 60, even 80 km a week and finding they can't recover from it and adapt. You may realise you only need to run 20 to 30 km a week to get through a 70.3, and that's a really important point.
Write down your resources
Sit down and write this out. Let's be realistic: what resources do I have? Time and availability, for a start. What's my diet like - does it need cleaning up? That's your priority, along with sleep and eating to support the training.
The training is hard, and it can be tricky, certainly in the third phase. You'll start to lose weight, because you're building your zone 2 and burning a lot of body fat. You're going to get tired, and that leads to grumpiness and mood changes. Your partner says, "Gosh, you're so obsessed with training - what about us?" and then you get resentful because they're not supporting you. Totally been there. We do get quite obsessed, and you live and learn.
2. Block 1: Build Your Aerobic Foundation
Say you've got six weeks for this phase in an 18-week build. If you have less time, just shorten the foundation phase. It's called many things - foundation phase, general conditioning - but the most important outcome is to build aerobic efficiency.
The more time you spend in an aerobic block, the better you get at using fat as fuel and the more you develop your mitochondria, which are your energy source. You become efficient: your body adjusts to the training and lays the foundation, so when you do the harder work down the line you have the durability. This is where people go wrong, so be patient - we're not chasing speed.
I'm working with someone at the moment whose run heart rate we're trying to bring down. After about six or seven weeks it just dropped, and the pace came down with it. But in the first three or four weeks it was definitely frustrating, because we'd redesigned the zones. We're building from the ground up. The longer you spend here, the better your durability and the better you're able to absorb work. You're only as good as the adaptation to your training, believe it or not: you break your muscles down, you break your energy pathways down, you rebuild, and that's when you get fitter.
Fix your movement patterns and imbalances
The foundation block is also where we reinforce good movement patterns and sort out imbalances. You can spot left and right imbalances by standing in front of a mirror and doing some single-leg balance work and head rotations. Look at your posture, too: whether you lean to one side, or stand with a sway back or a low lordotic curve in your lower back. (Females tend to have a bigger curve and a different anterior tilt of the pelvis - that's just anatomy.)
Most of us are tight in the quads, hip flexors and the front of the body, and the posterior chain isn't very activated - which is what we need for running, with its hip flexion and hip extension. Biking is all hip flexion and really quad dominant, so when you start to run you're all closed up.
Strength work and recovery weeks
Strength work is key throughout the plan, and I'd try to implement it lightly, twice a week. It builds resilience and durability, and it creates discipline.
In the first six weeks you'll probably find the first three okay, and from three weeks onwards you'll get quite tired. Build in a recovery week if you need to. You don't need the old way of doing it - three weeks on, then an active-recovery fourth week. It's about layering week upon week without pushing the needle too far too quickly, and you'll ebb and flow. Track your HRV (heart rate variability): if you're absorbing the training, you'll see it rise steadily over the weeks. If it trends down for a few weeks, you need to back off and let it come back up.
3. Block 2: Build Volume and Controlled Intensity
Block 2 is where things get a bit more exciting: we build some volume and start to add intensity. It's also where things can go pear-shaped for some people, because they do too much too soon, with too much frequency of intensity. One day they do an intense session, the next day another, then a day off, then another, and they end up racking up four intensity sessions a week. So keep the intensity controlled.
You maintain the strength work from Block 1 and increase your volume by perhaps one to two hours a week. That means sprinkling a little extra onto the end of each session, so sessions become slightly longer. That increases fatigue, which builds durability and gets you used to how you're going to feel in a race. It's all controlled - pace and intensity. You can use heart rate monitors, power or pace, but if you don't understand those metrics you're shooting into the wind, and you might need to dive a bit deeper into them.
Think of this block as controlled chaos: functional overreaching, which is managed and specific. It's not about smashing yourself, because one hero day doesn't make you better - I learned that the hard way, years ago. Big weekend, big day, then Monday and Tuesday are an absolute write-off.
Your first race-specific work
This is your first real exposure to the demands of your race. We know you'll be on the bike for anywhere from two and a quarter hours, if you're very quick, to three and a half, probably in a road position, or on a TT bike. So it's a controlled, tempo, zone 3 type effort, and we need to move towards 15-, 20- and 30-minute repetitions. You get race exposure with controlled pace and intensity, and you build fatigue.
Managed fatigue is different from just being tired all the time. We also learn what the body can handle, which teaches the body to handle more. So by the time you reach the race-preparation phase - the last five to six weeks, with the taper, in an 18-week plan - you'll be quite bulletproof.
4. Block 3: Race Specificity and Race Prep
Even if you're not trying to race - to use that strong word - you need to condition your body as best you can for the demands of the race. I think a lot of us ignore that and turn up unprepared, feeling like we trained for 16 weeks and still not performing to our potential. This is where we go from fit to prepared. It's one thing being fit, and most of you will be fit all year round, but being prepared is completely different. We sharpen the axe: sessions become more specific.
We also bring in more open water. There's a 99% chance your race is open water, so don't try anything new on race day. Plenty of people turn up having only ever been in a pool - plenty have done their first 70.3 without even dipping a toe in open water, let alone doing a sprint triathlon. (More on race-day errors in 5 Beginner 70.3 Mistakes.)
Swim: longer reps at threshold
We're not trying to break records in the swim. I always say we want to get out of the water as fresh as possible without burning much. Your half Ironman swim is roughly around threshold pace. So build from 100s and 200s, where most people tend to stop at about 200 m of threshold work - that burn, but not super hard - towards longer reps with shorter rest, accumulating sets like 5 × 400 m. Most people can't manage holding threshold for that long because they haven't conditioned themselves. I'd bring in a lot more threshold work in the swim, with longer reps, so you build fatigue and resilience.
Bike: longer power-based intervals
You don't have to ride 90 km in training. Even 70 to 85 km builds fitness, and it's low impact. The efforts are 20 to 30 minutes long, ridden at a pace you feel you could sustain for the full 56 miles (90 km). There's a specific range: you might ride above your race effort for 20 to 30 minutes, and the next time you come back to it, ride a little below. You play with those paces. There are different ways of slicing the cake, and it comes down to how conditioned you are by your last block and how early you started.
Run: short brick runs
With the run, we start to bring in brick runs - runs off the bike - more regularly. I'd keep them short, because we just want to improve muscle memory and firing patterns. When you get to the race, you're then so used to running on slightly heavier, tighter quads, and you've built leg speed on tired legs. You support the adaptation by doing what you're going to do. If you go and do 15 km off the bike, you'll just dig a hole.
So shift the training from generalised tempo runs, for example hilly runs on fresh legs, to more brick runs - ideally at least twice a week, though once is fine - so you get used to the transition.
That final block is probably the most important. You can turn up fit and still not feel like you're executing. This is where you turn your fitness into performance - and that's performance for you, which doesn't mean you're going to try to win the race.
How you fit these blocks into your Monday to Sunday depends on your life. Most people work Monday to Friday and train a little more at the weekend, but some work shift patterns and get the luxury of a mid-week long ride, which I sometimes do, keeping the weekends freer.
5. How Many Hours a Week Should You Train for a 70.3?
I know some of you are thinking: how much should I be doing? I'd say a beginner is in their first year, an intermediate has two to three years of triathlon (and might still be doing their first half Ironman), and an experienced athlete is chasing performance. There's nothing set in stone - this is a rough guide I use for most of my athletes, and it also depends on training age.
- Beginner: 6 to 8 hours a week
- Intermediate: 8 to 12 hours a week
- Performance focus: 12 to 16 hours a week
Beginner: 6 to 8 hours
That doesn't sound like much - you might think, "but a ride is three hours." Remember, it's week in, week out that builds fitness, endurance and resilience, and consistency leads to a better race. Over 18 weeks you'll have some weeks where you pick up a cold or some niggles, or big work deadlines mean the hours drop. If you can hit this, you'll absolutely nail a 70.3 and finish. You're not chasing a time.
Intermediate: 8 to 12 hours
A lot of you fall into this group because you're already comfortable doing eight hours. I used to say 8 to 10, but I might push that out to 8 to 12. Some of us are normally at the low end, and 10 is fairly manageable. I've done a lot of Ironmans averaging 12, but most weeks were 10: you plan for 15 and actually hit 10 or 12. For a half Ironman you can get a lot out of this, because you're not doing intensity every day.
Two high-quality intensity sessions a week is plenty. Anything in the severe domain - above your second threshold point - counts. Your first turning point is easy, conversational effort. Your second threshold, otherwise known as anaerobic threshold or your FTP, is what you can sustain for 45 minutes to an hour on the bike or the run. Anything above that is efforts of three, four or five minutes at around 90 to 95% of your max. You only do two of those a week, spread across the sports - for example one swim and one bike, or one bike and one run. It adds up over the plan. The rest is zone 2 work, and in the race-prep phase it's a lot of zone 3 with much less intensity. (For more on structuring a week around limited time, see Train Smarter, Not Longer.)
Performance focus: 12 to 16 hours
Here you'll put in extra duration, do more biking work - because that's where you get your gains - and keep your running really controlled. If the run is your weakness, you need to protect it, which means lots of supporting elements: quite a lot of single-leg work, and perhaps a little more physio to protect your movement patterns.
If the swim is your weakness, increase your frequency in the last block rather than trying to swim longer. That generally sorts out a deficiency in the swim. It does take a lot more time getting to and from the pool, but I'd start early, because swimming is technical. You can't build technical elements during a race-specific phase, which is more about open water and getting used to the wetsuit.
Be clear about what you're improving
Clarity is everything. What are you trying to improve? Don't try to work on all of it at the same time. It's one thing I tell my coached athletes: if we're on a swim block, don't expect to see much happening in the run or the bike. Run training really affects your swim, and so do long hours in the saddle - your swim times will be sluggish. That's not because you're losing fitness. Fatigue carries over, and the water is where you feel it. It's super dense, and most triathletes aren't very proficient swimmers - we're average, or quite new to the sport, and we haven't had a history as a youngster.
Frequently Asked Questions
How long should a 70.3 (half Ironman) training plan be?
Around 16 to 18 weeks works for most people, split into three blocks: a foundation block of about six weeks, a block that builds volume and controlled intensity, and a final race-specific block of five to six weeks, including the taper. If you're short on time, shorten the foundation phase.
How many hours a week do I need to train for a 70.3?
As a rough guide: 6 to 8 hours for a beginner, 8 to 12 for an intermediate athlete, and 12 to 16 if you're chasing performance. It's week in, week out consistency that builds fitness and resilience, so a beginner who hits 6 to 8 hours across 18 weeks will absolutely finish.
How much intensity should I do when training for a half Ironman?
Two high-quality intensity sessions a week is plenty, spread across the sports - for example one swim and one bike, or one bike and one run. The rest is mostly zone 2, and the race-prep phase is largely zone 3 with much less intensity. Racking up four intensity sessions a week is the classic mistake.
Do I need to ride 90 km in training before a 70.3?
No. Even 70 to 85 km builds fitness and is low impact. What matters are the efforts within the ride: 20 to 30 minutes at a pace you feel you could sustain for the full 56 miles (90 km), ridden slightly above your race effort one week and slightly below the next.
How often should I do brick runs for a 70.3?
Bring them in more regularly in the final block - ideally twice a week, though once is fine. Keep them short: the aim is to build muscle memory and leg speed on tired legs, not to dig a hole with a 15 km run off the bike.
Final Thoughts: You Don't Have to Build It Alone
Building your own 70.3 plan doesn't mean doing it alone. I've helped hundreds of athletes achieve goals they potentially didn't think they could, including qualifying for the world championships. But the main thing is simply to arrive at the start line fresh, not fatigued and, ideally, not injured. Those are the athletes who succeed - the ones who get a personal best or do better than they thought they could.
They don't guess. They follow a structure, and they train smartly, knowing when to pull back and when to push, because tightness can be misleading and a lot of it is just sleep. Stay consistent. If this has helped and you'd like more guidance, get in touch and let's chat!
