What is a Triathlon? The ultimate beginner’s guide to swim/bike/run

Your detailed guide to getting started in triathlon. It's swim, bike and run 101.

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You might have heard friends talking about it, you might have caught a glimpse of an exciting spectacle at the Tokyo Olympics, and you are looking for your next challenge, but what is a triathlon?

Fear not, we have you covered with an in-depth guide to a unique sport which combines three very distinct disciplines.

Our aim is to put the knowledge in your hands and give you enough information to begin your triathlon journey.

Swim, bike and run

In its simplest form, a triathlon starts with a swim, which is then followed by a bike ride and is finished off with a run (or jog/walk, depending on how the race plays out for you!).

There are various forms of multi-sport events (such as duathlon, aquathlon, pentathlon), and even triathlons can vary greatly in terms of distance and settings or conditions (see below).

However, a triathlon event is classically a swim, bike, and run, and in that specific order.

What is transition?

To master triathlon there is a crucial fourth discipline, where time can be gained or lost. It’s called transition and there are two in each race – T1 and T2.

T1: After the swim we come to the first transition, known as T1. You exit the swim and move as swiftly as possible to mounting your bike and starting the second stage of a triathlon. It’s a good idea to practise everything; putting on your helmet and running or walking with your bike – literally every second counts.

It’s also worth spending time before the start of the race checking where your bike is located in relation to where you enter T1 after the swim.

T2: After the bike leg there is another transition called T2.  Here you need to dismount your bike and set off on your run. It’s important here to make sure you are not going too fast to safely get off your bike. Again, check out in advance where you need to rack your bike and the quickest route to the exit.

The length of the transitions in a triathlon vary from race to race. The only true constant is that with practice you can save a lot of time, potentially minutes, and improve your overall finishing time and position.

Triathlon distances

There are several different distances for triathlon – with the most famous being Ironman. But how long is an Ironman and how long are the other distances? Again, we have you covered.

An Ironman triathlon is the full distance for the sport and a pretty gruelling test. It is a 2.4-mile (3.8km) swim, a 112-mile (180k) bike and then a literal marathon (26.2miles or 42.2km) to finish. Total distance 140.6miles or 226km. A half-distance triathlon is held over 70.3 miles or 113km.

An Olympic distance triathlon (like the ones you might have watched in Tokyo in 2021) is held over a 1500m swim, a 40km bike and a 10km run. Olympic distance is also known as the standard distance for triathlon.

There are other distance options for triathlon – going even shorter than that Olympic distance down to sprint races. Basically there are tons of ways you can get started in the sport without diving in at the deep end in an Ironman race.

There are a number of famous organisations which stage triathlon races – headed by IRONMAN (the company not the distance!). IRONMAN holds races over full distance, the 70.3 half distance and also some at Olympic distance.

IRONMAN stages races all around the world all year round, with athletes desperate to cross the finish line one day to hear the immortal words “You are an Ironman”.

The Challenge Family meanwhile has a portfolio of internationally acclaimed full and middle-distance races. In addition, and often with far cheaper race entry costs, there are many local races hosted by triathlon clubs or smaller race organisers.

As with most things in life, it’s worth starting small and building up in terms of triathlon distances. We’d suggest finding somewhere local to get your feet wet, and build up from there.

Getting started in triathlon

There is a triathlon for everyone. Depending on your strengths and sporting background, along with your appetite for a challenge, particular race distances and conditions may appeal to you.

There are a number of race listing resources globally. In the UK, the British Triathlon website is a good starting point, which will feature all of the events registered with the national governing body. British Triathlon also supports GO TRI, a resource for people who are very new to the sport.

Another great way to get started in triathlon is to join a triathlon club. It’s worth checking to see if you have one locally. Much easier when things are close by.

Many triathlon clubs cater for beginners through to experienced triathletes. You’ll be surrounded by like-minded people who are willing to share their experiences and advice.

In particular, taking part in coached swim sessions can be very beneficial for beginners; and, bike and run sessions with other people can really push you forward.

How much does it cost to do a triathlon?

There is no one easy answer to this question. It depends on the race and the distance.

The costs can be daunting but there are many affordable options if you do your homework (see above).

There is often a direct relationship between a race’s entry costs and the size of the event, the length of the race, the picturesque nature of the location, the event publicity, and the ‘free’ goodies (for example, bags and T-shirts).

IRONMAN-branded events are the top end of the scale and entry fees can be more than £500 or $700. You are in part paying for the experience of an iconic race location, participating in a huge event, and the opportunity to be told ‘you are an IRONMAN’.

In contrast, there are many races with lower fees which have received really favourable reviews, for example the Outlaw-branded races in the UK.

The Castle Series events have been running for more than 10 years, and they try to create a festival atmosphere. For example, at Hever Castle (in Kent, UK) in addition to adult races across various distances there are numerous youth races, accompanied by live music, food vans, and other entertainment. The price is c. £100 for Olympic distance.

At the opposite end of the scale to IRONMAN, there are way cheaper races which are still really well organised. These can cost as little as £10 or $15 to enter.

What kit or gear do I need for triathlon?

If you like tech, triathlon is the gift that keeps giving. However, it is possible to take part in triathlon without breaking the bank. Remember that entry fees are not your only cost.

To race you will need the following kit as a bare minimum:


  • Swim cap, often provided by the organiser
  • Swim goggles
  • Swimsuit or trisuit

If the race is in open water, you’ll also need a wetsuit – though you can hire one if you don’t fancy buying one yet.


  • Shorts and a top – can be normal shorts and T-shirt or bike shorts and a jersey
  • Helmet
  • Bike
  • Cycling or triathlon shoes – you can just use trainers
  • Socks


  • If not wearing a tri-suit, you might want to change into a new top and shorts.
  • Trainers

Race numbers for the bike and run are normally provided by the race organiser.

Coping with the conditions

A crucial factor when determining what triathlon to do, in addition to the distances, is the race’s terrain and conditions.

The Swim: The triathlon swim can be in a pool or open water – big difference.

A swimming pool-based triathlon can be a great place to start if you are not particularly confident in the water. Equally, they are a good option if you are looking to compete at the start or end of the season when open-water events would be too cold.

Pool-based swims are often 400m in distance, but can be shorter or longer, and the length of the pool will vary from event to event. Swimmers normally set off individually at timed intervals, but how the swim is navigated varies (for example, moving from lane to lane in a zig-zag style or completing the swim in one designated lane).

You may feel of course that the real challenge is in open-water swimming. Open-water swims can be held in a lake, river, or the sea. A lake swim is likely to be calmer than a river or sea swim, where you obviously have to contend with waves and the current.

Open-water swims normally have mass starts, broken up into waves (at larger events, it is not uncommon for a wave to include around 100 athletes).

The Bike: The vast majority of triathlons are non-drafting and held on open roads with traffic. However, closed circuits (racetracks) are becoming more popular.

Triathlons can also have off-road bike sections, which will normally require the use of a mountain bike (British Triathlon’s competition rules only permit mountain bikes for cross triathlon). Events with off-road bike sections are commonly referred to as ‘cross triathlon’.

XTERRA is the main international series of cross triathlon and, rather than road riding and running, has off-road mountain biking and trail running.

The Run: Similar to the bike options, a run can be on the road, off-road, or commonly a bit of both. Your choice of footwear will depend on the terrain. Importantly, a 10k run on a flat road may be much less taxing than a 10k on an undulating and uneven off-road route.

What are the rules for triathlon?

All sports have a rulebook, and triathlon is no different.

Here are a few of the most important ones if you’re a beginner:

  • On arriving at the race your bike will be inspected (as well as a check that your helmet fits correctly). The bike must be roadworthy and safe. Of particular note, your handlebars must have bar ends/plugs in place.
  • Buoyancy aids are not permitted in the swim. In races where wetsuits are not worn, during the swim clothing is not permitted below the knee. This means that if you wish to wear calf guards these will need to be put on after the swim.
  • A bike helmet is mandatory. In T1 you must put your helmet on (and fasten it) before you remove your bike from the rack. In T2 you must have re-racked your bike before you take off your helmet.
  • On exiting T1, you must not mount or get on your bike until you have passed the mount line – most often this is a line drawn on the road with marshals closely monitoring the line has been crossed. Similarly, upon returning to transition you must dismount your bike before crossing the dismount line.
  • Depending on the race you enter, the bike leg will be either non-drafting or draft-legal. So what is drafting? Basically it’s riding close behind somebody else which will then give you an advantage thanks to the natural tow it gives you. So if your race is non-drafting, that’s what you absolutely cannot do. If you do, you could get a time penalty or even be disqualified.
  • On the bike, when riding on open roads, you must comply with the laws of the road, including not crossing the white-line onto the opposite side of the road.
  • Unlike many running races, headphones are not permitted to be used during any part of a triathlon.

How did triathlon begin?

For many, the attraction of triathlon is the variety and the challenge of mastering three sports – taking on one simply isn’t enough! It may not be a surprise therefore that an athletics club holds the accolade of kick-starting triathlon as we know it.

Modern triathlon emerged in the early 1970s, specifically on 25 September 1974 at an event hosted by the San Diego Track Club. The event was intended to act as an alternative to hard track workouts and comprised a total of 6 miles of running, 5 miles of biking, and 500 yards of swimming. Forty-six people took part and the organisers used car headlights to help direct those finishing after sunset.

Shortly afterwards, Judy and John Collins (who had raced in the San Diego Track Club’s event and had moved to Hawaii from California in 1975) were pivotal in organising the first Hawaiian IRONMAN Triathlon on 18 February 1978.  Ironman racing was born.

Triathlon’s popularity increased exponentially over the following years.  The International Triathlon Union (ITU) was founded in Avignon, France, in 1989 and in that same year the ITU’s first official world championships were held. The standard Olympic distance was based on existing Olympic distances for individual sports, namely 1500m swim, 40km bike, and a 10k run.

Triathlon landed in the mainstream with its debut at the Sydney Olympics in 2000. The success of the Brownlee brothers at London 2012 took things to a new level in the UK.

Written by
Chris Hovenden
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