How to improve your Ironman swim

Just because the swim in a long-distance triathlon is less than 10% of the total doesn't mean you should ignore training for it in favour of the other two disciplines says Andrew Potter. Here he explains the importance of a successful Ironman swim and how to get faster...

Ironman UK 2014 – the swim

The Ironman swim (3.8km) is less than 10% of the race, and it’s this fact that often encourages age-groupers, who are good bikers and/or runners, to move up to the longer distance. If you asked age-group Ironman (IM) athletes to rate the relative importance of the disciplines, it may be something like this: 42% run, 44% bike and 14% swim. Consequently, many athletes spend most of their time focusing on everything but the swim. However, the swim is as significant a part of your Ironman race as the bike or the run.


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How to swim the 3.8km of the Ironman swim leg

Clearly, at 3.8km the IM swim is much further than the Olympic-distance swim at 1.5km. But when you think about it, they’re not that different – in essence they’re both relatively long, aerobic swims. The real differences emerge when you consider the following factors: the size and physicality of mass starts; the anxiety levels at the start of an Ironman; the impact of bad pacing on energy levels; the pure complexity of tactics with so many swimmers around you.

Some say that the long-course swim, while being 10% of overall distance, is 80% of the emotion. This offers an insight into why you need to plan the swim properly both in terms of training and on the day.

Gain free speed

Given that you’ll spend less time training for the swim than the other disciplines, increasing your weekly swim total by a relatively small amount – for instance, swimming 5hrs instead of 4hrs – will see a dramatic reduction in your swim leg, potentially cutting your swim personal best by up to 20mins. What would be the extra training time required to achieve that by adding extra biking or running?

Quite simply, the swim should be more about the ‘how’ than the ‘how fast’. Unlike the shorter-distance events, a long-course swimmer needs to exit feeling fresh and ready to go, so you can’t afford to use excess energy. Everything about your training and racing should be focused on efficiency.

Swimming is a highly technical sport and, bizarrely, the faster swimmers will use less energy than the poorer swimmers. Hence, a small extra investment in time and technique, aimed at delivering energy savings in the race,
will yield bonus energy for the athlete as the race unfolds. Technique improvement therefore equals free speed.

Training pointers

The aim of the average age-group triathlete shouldn’t be to do the minimum training to last the distance but to think like, and become, a swimmer. Many age-groupers train too hard on laps and without enough emphasis on basic skills, which would improve their 3.8km efforts. We haven’t room here to run through the front-crawl technical hit-list but, for now, make the following three areas your priority…

Sub-1hr swim session: Long-course peaking


Typically, slower swimmers sink at the back. To help rectify this, work on your balance. It’ll make a large speed difference due to the reduction of drag – the biggest single factor that limits forward propulsion. And those of you who think you can just take advantage of the wetsuit’s buoyancy, stop right there: some IM swims are non-wetsuit so don’t rely on neoprene for improved support!

How to prepare for a non-wetsuit Ironman swim leg

How to stop your legs from sinking in the swim

Swim breathing for the Ironman

So many age-groupers use one arm to pull forward and one arm to lean on for breathing. The problem is this leads to lifting up at the front, and a rise of just 25mm will cause the back to go down 175mm. Breathe properly and you’ll soon get streamlined.

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The last biggy for the majority of age-group swimmers is the grip. We want to promote a slower, longer, more energy-efficient stroke for distance swimming, so we need to be pulling on the water all the way through the stroke. This is achieved by a gradual acceleration through to the fast finish (or push) past the hips to the thigh (think ‘slow to fast’). So many athletes grab the water too aggressively and then their hands/arms slip through the water to a short finish.

Front crawl technique: the key compenents

How to streamline your swim

Little and often 

There’s no need to knock out 3.8km every time you train. You should swim intervals, with the sets between 150m and 400m for 90% of the time. By keeping intervals manageable, you’ll have a better chance of focusing on technique. That said, the Ironman is a one-hour-plus swim and, therefore, the overall session length should reflect the endurance swim fitness you’ll need.

You also need to learn pace, so get used to using your watch/clock all the time. You should know what 80% feels like versus 95%, as well as knowing your swim split times for any distance and effort level. Six weeks from the race, you should be swim fit enough to handle one-and-a-half-hour sessions (4km), with occasional swim set efforts of 3 x 1km or 4 x 750m to get used to pacing and continuous effort. Also by this time, ideally you’ll be swimming a minimum of four times per week, where you’ll cover about 12km.

The IM swimmer also needs to practise open-water technique – poor technique will again cost heavily in energy and speed. Practise swimming straight, as well as focusing on sighting without lifting your head or body too much at the front, because this makes you sink at the back.

Open-water swim technique: the key components 

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Open-water swim tactics

Also, practise navigation and swim drafting skills. If the race is sea based, practise in the sea where possible. If you’re expecting a non-wetsuit swim, occasionally train in open water without the neoprene. Try and fit in three open-water sessions over each four-week period in the 12 weeks prior to the race.

Swimming on the day

The long-course swim is the most physical event in all of triathlon. All IM races are mass starts of 1,000 to 1,800 athletes or more. It’s a key feature of IM events and, as such, strikes fear into most people. Apart from dealing with the sheer numbers of swimmers around you, you need to approach the swim in a way that minimises your anxiety levels, which can drain you of vital energy. To do this you must prepare, have a plan and keep the focus on yourself during the swim.

Reconnaissance, and preferably practise on, the course. It’ll give you both information (currents, waves, sighting aids…) and confidence on race day. Also, watch swim starts from previous races on YouTube. Look at the swim times and position yourself accordingly. Not everyone is optimistic about their swim, but remember: the focus is on the ‘how’ and not the ‘how fast’.

On race day, it’s integral that you try and control your adrenaline, only going out hard if you’re a good swimmer looking for clear water. Otherwise, controlling your swim is paramount to saving energy and having a good swim time (80% effort, 100% speed).

In your warm-up, focus on regulating and relaxing your breathing, as the adrenaline will have you breathing too hard and shallow. Practise doing some breathing exercises on your back; visualise the start; swim with good technique.

The start itself can be physical and the worst place to get trapped is in the middle, halfway back. Unless you’re going sub one hour, stay off the racing markers, which are usually on the inside of the course, because this is the busiest area.

Whether you put your goggles over your hat or under is a personal choice: on top, they’re easy to re-position if leaking after a knock; underneath, you don’t lose them if you’re kicked. Practise as you would race.

After the start, the turning buoys are the next most physical place – there’s always a mass of people (even after 1.9km for a halfway turn). So think ahead; don’t get trapped on the inside because you’ll lose all rhythm and use up valuable energy. Swim slightly wide to make the most gains.

Best technique for swimming round buoys in a triathlon

The swim is long and it’s easy to lose focus, so this is where your longer pool sessions and interval pace training will pay off handsomely. Keep focused on your next 500m and swimming smoothly and efficiently. As you tire, the stroke tends to shorten, and this is where the focus on technique in your training comes in. Finish the stroke, keep the recovery relaxed, and really channel your rhythm and breathing.

The pay off

So, you haven’t obsessed about your final swim time but you have exceeded expectations, perhaps even enjoyed the swim, and will emerge with more energy and, equally importantly, with a positive mindset for the rest of the day. You’ll race 20-30mins faster than if you had stressed and fought your way through the swim.

Top 10 Ironman swim training tips

Plan your sessions.

The focus of each session should be at least 20%-25% on technique.

3 Swim intervals and know your watch.

4 Keep interval lengths down to help you maintain technique.

5 Increase length of main swim sets gradually through the programme so you can handle a 4km swim session eight weeks from the race.

6 Don’t swim long too often – occasional 4 x 750m or 3 x 1km sets for pacing and confidence are fine.

7 Use swim aids to break up the training and add variety.

8 Improve key technique areas such as: balance; breathing – bilateral, not leaning on the hands; slow to fast finish; kicking – lightly and efficiently will reduce drag, especially in non-wetsuit swims.

9 Train in open water as part of your meticulous programme.

10 Open-water sessions should include warm-ups and breathing exercises, open-water skills (sighting, navigation, drafting) and steady-pace swimming.

Ironman swim checklist


Know the course Familiarisation will make navigation easier. Ideally swim the course before the race. This will increase confidence, while acclimatising you to water conditions and giving you an idea of ‘sighting’ landmarks.

Research past races Watch previous events and note the spread and pattern of swimmers. If you’re a sub 58min swimmer, you can be behind the top swimmers and get sucked along; if you’re a slower swimmer, you want to avoid certain areas like the racing line or the marker buoys.

Know local conditions If it’s a sea swim, find out about the currents and plan accordingly.

The start and the race

Start position This is dictated by your swim speed. Sub 58mins, go at the front near the racing line; 65mins, a third of the way back from the racing line; 70-75mins, halfway back from racing line; 75mins-plus, 20% behind main pack.

Tactics Fast swimmers should go out reasonably hard to find clear water sooner and then settle into a slower pace; everyone else should conserve energy and work their way into the swim.

Drafting Use the technique of drafting to conserve energy. After 15mins you should find
a decent pair of feet.

Navigation Don’t rely on people; use your in-depth research and sighting aids from
course reconnaissance.

Around the turns Don’t fight for position – swim wide, keep rhythm and conserve energy.

Pacing and stroke Steady and even, relaxed and efficient. Focus on your stroke.



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