HomeTri LifeAbout TriathlonWhat Is An Ironman 70.3?

What Is An Ironman 70.3?


All you need to know about Ironman 70.3, the half-iron distance triathlon covering a 1.2-mile swim, 56-mile bike and 13.1-mile run.

An exhilarating mix of endurance and speed, Ironman 70.3 is one of the most popular race distances in triathlon. These events challenge you with a 1.9km (1.2-mile) swim, 90km (56-mile) bike and 21.1km (13.1-mile) run – for 70.3 miles in total, half the full Ironman distance.

While Ironman 70.3 races – also known as half-Ironman or middle-distance – are the perfect stepping stone for athletes who are building up to take on an Ironman, they’re great races in their own right with an effort level that’s probably closer to an extended Olympic distance race than the lower intensity of longer race formats.

Why do an Ironman 70.3?

Breaking the Ironman 70.3 down into its constituent disciplines, it’s easy to see why the popularity of this format has soared. Adding just 400m to the 1.5km of Olympic-distance races in the water, the swim isn’t too much of a step up for athletes craving a longer race.

At 90km, the bike takes up the biggest proportion of the event, which suits many triathletes. It’s is a serious endurance effort but can still be ridden at a good tempo, suiting those strong-legged riders from a cycling background.

Finally, the half-marathon run blends a concentrated physical and mental effort to overcome the distance. Strong runners excel here, the many half-marathon events on the calendar providing ample opportunities for training races if you’re looking to run fast during your 70.3.

Ironman 70.3 Calgary finishers medal
For some athletes, crossing the line to earn a finisher’s medal makes an Ironman 70.3 worth it. (Photo: Dawn, Creative Commons)

With all this in mind, Ironman 70.3 races offer the perfect blend of training versus racing for many athletes. Getting fit enough to compete doesn’t have to take over your life but nor is the race over in the blink of an eye, so the finish-line satisfaction is immense and addictive.

Being run by Ironman, the 70.3 race experience is superb and you’ll be joined by thousands of other athletes, which helps to create a real spectacle of an event and builds an incredible atmosphere. If you’re looking for alternatives, the Challenge Family brand is known for its fantastic competitor experience and offers a great selection of middle-distance events in fabulous locations, particularly around Europe. If you prefer a little less pomp and ceremony – and want to save money – there are plenty of grassroots middle-distance events on the race calendar too.

Ironman 70.3 history

While the first official Half Ironman took place in the UK in 2001, it wasn’t until 2005 that the Ironman 70.3 name was coined, also in the UK. The following year saw the inaugural Ironman 70.3 World Championships, held in Clearwater, Florida, where the event stayed until moving to the heat of Las Vegas, Nevada, in 2011. Since 2014, it’s moved location each year, giving the world’s best athletes to test their abilities against different courses.

The popularity of 70.3 racing has meant colossal growth for the series with over 100 Ironman 70.3 events on the global calendar. Each event has a number of slots for the fastest athletes in each age group to qualify for the Ironman 70.3 World Championships.

The Ironman 70.3 Swim

As in Ironman, the 1.2-mile (1.9km) Ironman 70.3 swim only ever takes place in open water (rather than a pool), be it the sea, a lake or, very occasionally, a river. It’s here that the shared nervousness, camaraderie and excitement of 2,000 athletes sets an electric atmosphere that lasts the whole day. There are a few different swim-start types to contend with.

Mass starts mean everyone starting at exactly the same time and whether you’re already in the water or have to run in from the beach when the air-horn blasts, it’s a chaotic, adrenaline-fuelled thrashing of arms to find clear water. Seeding yourself is essential – if you’re a weaker swimmer and line up at the front, you might get swum over while stronger swimmers will be held up by crowds if starting too far back.

Occasionally there are wave starts, usually arranged by age groups, which make the mass start a little less manic purely because there are fewer athletes vying for the same area of water.

Ironman 70.3 swimming
The 1.9km swim is the start of an exciting day of Ironman 70.3 racing (Photo: Triangleevents, Creative Commons)

Without a doubt, the most well-mannered start protocol is the rolling start. Here, you form an orderly queue behind the start line and once the gun goes off, you follow the other athletes into the water, your personal race time beginning as you cross the timing mat. While it’s certainly first-timer friendly, faster athletes may find rolling starts frustrating as if you’re gunning for a high placing in your age group, you don’t know whether or not an athlete you pass – or an athlete who passes you – is actually ahead or behind on time. 

Swims at the 70.3 distance can be one or more laps and individual laps sometimes feature an Australian exit, where you’ll have to drag yourself upright and run across the waterside before continuing the swim. In the case of Ironman 70.3 St. Pölten in Austria, this actually involves swimming a lap in one lake before running to another to finish the swim. It’s certainly makes spectating more exciting, but as an athlete, it can be a dizzying, wobbly-legged trot as the blood rushes back into your legs.

Wetsuits are compulsory in 70.3 races when the water temperature is below 16°C. Then there’s the optional range up 24.5°C. Race organisers have discretionary powers to allow wetsuit use up to 28.8°C, however, athletes who make use of wetsuits in such situations won’t be able to compete for age-group podium awards or qualification for the 70.3 World Championships. Depending on your tolerance to the water, at temperatures over 20°C, wearing a wetsuit can cause you to overheat, so if the water temperature is quite high, get a few practise swims in before deciding on your race-day strategy.

T1 – Swim to Bike Transition

Whereas many smaller triathlons give space alongside your bike for your kit, transition areas in Ironman 70.3 events utilise coloured bags in which you store your gear for each discipline. These are then hung from numbered pegs in huge marquees at transition check-in. With thousands of bags hung in ordered rows, it’s essential to run through exactly where your bag is at check-in.

Upon finishing the swim, you’ll find the bag with your corresponding race number and run into the change tent to get your bike gear on. Your wetsuit, hat and goggles go into the empty bike bag, which you can toss unceremoniously onto the pile before heading out to find your bike.

As with the bags, pre-race run-throughs will help you to quickly find your bike. Using a fixed object outside transition to orientate yourself – such as a tree, lamppost or flag – can help you quickly navigate to your pride and joy.

The Ironman 70.3 Bike

The 56-mile (90km) Ironman 70.3 bike leg is a distance not to be underestimated, especially considering the half-marathon run to come afterwards. You’ll need a good endurance base and a solid nutrition strategy to keep your body fuelled.

Ironman 70.3 courses can vary from very flat routes with minimal elevation change, such as 70.3 Texas, to spiky profiles with plenty of climbing to tackle before reaching T2, like 70.3 Nice. Flatter isn’t necessarily easier, however. On a hilly course, the climbs might make the legs sting, but the downhills give some recovery time. On a flat course, you need to be pushing a constant power for the entire duration, which is a challenge in itself. On the whole, stronger heavier athletes are better suited to flatter profiles whereas lighter athletes can make use of their power to weight ratio when the road turns upwards.

Ironman 70.3 hilly bike course
Ironman 70.3 bike courses vary from flat and fast to steep and challenging. (Photo: Dawn, Creative Commons)

Some courses are one long lap, such as Ironman 70.3 Mallorca, which minimises congestion on the roads. Others are multi-lap, which can help you mentally break the distance down and also makes a pre-race recce of the course a little easier. Official Ironman 70.3 events are usually held on closed roads, so you don’t have to worry about regular traffic – though the rules of the highway still apply. There will also be multiple aid stations to help you refuel and stay hydrated on the go.

Like almost all age-group triathlons, Ironman 70.3 bike sections are non-drafting. Under the Ironman competition rules, your front wheel must not be less than 12m from the front wheel of the rider ahead – around six bike lengths’ worth of space – unless you’re overtaking. If you do move into this zone, you’ve got just 25 seconds to overtake otherwise you’ll face a five-minute time penalty.

T2 – Bike To Run Transition

The bike leg finishes at transition where, after 56-miles in the saddle, you’ll gratefully hop off your bike at the dismount line, raring to get out onto the run. With the exception of split transitions – where T1 and T2 are in different locations, such as at Ironman 70.3 Staffordshire – you’ll return to the transition zone to rack your bike in the same spot.

Then you’ll grab your run bag from its hook and head into the changing tent. Volunteers are usually on hand to help you with your kit. You’ll put on your run gear, shove the bike kit into the empty bag and add it to the ever-mounting pile. With a regiment of portaloos in transition, now’s a good time to nip in before heading out onto the run.

The Ironman 70.3 Run

The half-marathon, 13.1-mile (21.1km) run is a tough distance to compete at, balancing the cardiovascular fitness of shorter events with the muscular strength and endurance needed for this longer run. Coming as it does after the 56-mile bike, the Ironman 70.3 run requires careful nutritional planning, expert pacing and practised mental strength.

Ironman 70.3 run
Multi-lap run courses can take you cruelly close to the finish line a few times before you finally get there. (Photo: Dawn, Creative Commons)

The terrain can vary greatly with some runs sticking to the pavement while others feature sections of grass or trails. Elevation change can also differ hugely, so check the websites for each event to narrow your search if you’re a demon up hills.

Ironman 70.3 runs are almost always multi-lap courses, giving friends and family spectating the chance to cheer you on several times. There will be plenty of aid stations along the way to help you manage your energy levels all the way to the finish line – and that incredible, addictive feeling of having conquered this tough triathlon challenge.

Ironman 70.3 Cut-off Times

As with most aspects of Ironman 70.3, the cut-off time is usually half that of full Ironman – but double check when you sign up as it can vary depending on wave starts. Typically, you’ll need to be able to complete the swim in 1:10, the bike by 5:30 from your start time and the run by 8:30 from your start time. If you go beyond the finishing cut-off, your time will not be recorded and nor will you receive a finisher’s medal.

Where Can I Race Ironman 70.3?

There are over 100 Ironman 70.3 events internationally and more are being added every year. The highest concentrations of races are in North America and Europe, though there are also events in South America, South Africa, Australasia, the UAE and Southeast Asia. View the entire 70.3 race series at Ironman.com.

How much does an Ironman 70.3 cost?

While Ironman 70.3 races tend to have fantastic organisation and a really great athlete experience, there’s no denying that you pay for that privilege. On top of the race fees, which are around £285 / €300 / $330, there’s also an eight per cent transaction fee to take into account. Many races do offer cheaper rates the sooner you sign up, but if an official 70.3 is too expensive for your liking, there are plenty of grassroots events available with entries costing less than half of the big races.

Triathlon Vibe
Triathlon Vibe
Triathlon Vibe is the home of triathlon training advice for beginner to expert triathletes. From sprint to Ironman, we share how to swim, bike and run stronger and faster.


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