Triathlon

A triathlon is a swim, a bike ride and a run, completed in that order, against a single clock that does not stop while you change between them. That last detail is what makes it a sport in its own right rather than three sports on the same afternoon: the transitions are timed, they are practised, and the ability to ride well on legs that have just swum — and run on legs that have just ridden — is a specific trainable thing that nobody discovers by accident.

The distances are standardised enough to plan around. A super-sprint or pool-based event is the gentlest entry, often with a swim of a few hundred metres. A sprint is the standard first race: broadly a 750m swim, 20km bike and 5km run. Standard or Olympic distance roughly doubles that. Middle and long distance — the branded ones people have heard of — go up to a full marathon at the end of a very long day, and are a different commitment in every sense. Exact distances vary between events, so read the entry.

The other thing worth understanding early is that the three disciplines do not contribute equally to your result or to your suffering. The bike takes the most time, the run usually decides the placings, and the swim is where nearly everybody’s anxiety lives — despite being the shortest segment by a wide margin.

Start here

A pool-swim or super-sprint eventIt removes cold, crowding and sighting all at once.

The real barrier

Open water, not fitness

What to practise that nobody does

Transitions, and riding then running

Bike required

A roadworthy one, not a fast one

1. 1

   Step 1: Enter a sprint or pool-swim race four to six months out

   An entry is the single most effective piece of training equipment in endurance sport. A date makes the training specific, and a sprint is far enough away to prepare for and near enough to stay real.

   You will know it worked when: A deadline, and a reason to swim on a Tuesday.

2. 2

   Step 2: Find out where your swim actually is

   Not how fit you are — how comfortable you are. Swim continuously in a pool and see what distance you can cover without stopping. Most beginners can run and ride further than they can swim, and the swim is where the training time should go first.

   You will know it worked when: An honest baseline rather than an assumed one.

3. 3

   Step 3: Get into open water deliberately, and with supervision

   This is a separate skill from pool swimming: no line on the bottom, no wall to hold, limited visibility, cold, and other people’s feet. Go to a supervised open-water venue rather than teaching yourself in a lake. The first session is unpleasant for almost everybody and much better the third time.

   You will know it worked when: The component that ends most first-timers’ races is no longer unfamiliar.

4. 4

   Step 4: Ride the bike you have, and make it safe

   Working brakes, correct tyre pressure, a helmet that fits. Do not buy a triathlon bike to find out whether you like triathlon. Almost any roadworthy bike will complete a sprint, and the rider matters far more than the machine at every level a beginner will encounter.

   You will know it worked when: You are riding rather than shopping.

5. 5

   Step 5: Practise brick sessions

   A ride immediately followed by a run. The first ten minutes off the bike feel genuinely strange, your legs do not do what you ask, and the only cure is having felt it before. Two or three of these before race day changes the experience completely.

   You will know it worked when: The run off the bike stops being a shock.

6. 6

   Step 6: Rehearse the transitions in your garden

   Wetsuit off, helmet on before you touch the bike, shoes, number. It looks trivial and it is where first-timers lose several minutes and most of their composure. Ten minutes of practice is worth more than a week of training here.

   You will know it worked when: The race stops containing a puzzle.

• A helmet that fits — Non-negotiable and the first purchase. Fit matters more than price; an expensive helmet worn loose is worse than a cheap one worn properly.
• Any roadworthy bike — A road bike is faster, a hybrid or mountain bike will finish a sprint, and a serviced secondhand bike beats a neglected new one. The bike is where the sport’s reputation for expense comes from and it is the easiest place to ignore that reputation.
• Goggles, and a spare pair — Goggles that leak in open water ruin a swim entirely. Find a pair that seals on you, then buy a second identical pair.
• A wetsuit — hired first — Triathlon wetsuits are cut for shoulder movement and buoyancy, not for warmth alone, and a surfing wetsuit is a poor substitute. Hire before you buy: they are expensive, fit is critical, and one race will tell you whether the sport is sticking.
• A tri suit — Worn under the wetsuit and for the whole race, so you never change clothes. Not essential — shorts and a top work — but it removes the most awkward part of transition.
• Elastic laces — The cheapest meaningful upgrade in the sport. They turn putting your running shoes on into a two-second job with cold hands.
• What can wait indefinitely — A time-trial bike, a power meter, race wheels, a carbon anything. These make measurable differences to people already near their ceiling and no difference at all to a first sprint.

• Draft-illegal is the default, and the draft zone has a size — Most age-group racing is draft-illegal, and the elite racing on television frequently is not — which is why this is the rule most often misunderstood. Where drafting is forbidden, the zone is defined: "The bicycle draft zone will be 12 metres long measured from the leading edge of the front wheel." You may enter it, but "must be seen to be progressing through that zone", with "a maximum of 25 seconds" allowed to pass. You are passed the moment another competitor’s front wheel is ahead of yours, and once passed you must drop back out of their zone "by continuously making rearward progress".
• What drafting actually costs — A time penalty on the first offence, scaled to the race: 30 seconds in a sprint or shorter, one minute at standard distance, two minutes at middle distance, three at long. Then disqualification — at two drafting violations in a draft-illegal sprint or standard race, and at three in a middle or long one. Non-drafting penalties are shorter: five to ten seconds at sprint distance for things like riding in transition or an uncorrected race-number violation.
• The helmet rule, which is where first races are actually lost — The helmet must be fastened from the moment you take the bike off the rack until after you have put it back, and — the converse, and the one first-timers are penalised for — "The helmet strap must remain unfastened in the Transition Area while the competitor is completing the first segment." Unclipping while still touching the bike is a time penalty unless corrected. Riding inside transition, including over the mount or dismount line, is the same.
• Wetsuits are decided by a thermometer, not by preference — Mandatory below 15.9°C at every distance and every age. Forbidden above 22°C for swims up to 1500m if you are 59 or under, and above 24.6°C if you are 60 or over or the swim is 1501m or longer. The water is measured an hour before the start, "at the middle and two other areas on the swim course, at a depth of 60cm", so the decision genuinely is made on the morning.
• And below 11°C there is no swim at all — "At temperatures below 11°C open water swimming in competition cannot take place." Between there and 14°C the distance is capped rather than the race cancelled: 1000m at 13°C, 600m at 12°C, 300m at 11°C. A shortened swim on a cold morning is the rules working, not the organiser losing their nerve.
• Outside assistance, and the friend with the drink — Outside assistance is a disqualification offence, and it includes somebody handing you a bottle or fixing your puncture. So is unsporting impedance — which the rules define to include "incorrectly racked cycles, discarded equipment and the use of marking devices in transition that impede the progress of others". Marking your spot with a towel is a real offence, not a folk rule.
• What gets a word rather than a penalty — A verbal warning is given where a violation is unintentional, about to happen, or has gained no advantage, and where the thing can be fixed — illegal or banned equipment, an exposed torso, an unfastened zip, and "Littering on the course unless disposed of in specified littering zones provided by the Event Organiser". If you do not fix it, the disqualification follows.

Triathlon is a well-organised sport with medical cover and marshals, and the great majority of races pass without incident. The risks that matter are concentrated at the start of the swim and on the bike, and both are manageable if you know they are coming.

• Transition areas are crowded and slippery and are a common site of minor injury. You are not permitted to ride inside them and the rule is a safety one.
• The bike leg on open roads is the highest-consequence part of the race. Ride to the conditions, take corners on wet descents at a speed you would ride alone, and remember that the field around you contains people whose bike handling is worse than yours.
• Hypothermia after a long cold swim is a real risk and it develops after you get out, not during. Dry clothing at the finish is not a luxury.
• Get a medical opinion before starting endurance training if you have a heart condition, are managing a chronic illness, or have been inactive for a long period. NHS guidance sets out what adult activity levels look like and is a sensible baseline to build from rather than jumping straight to race training.

Triathlon is one sport with a wide range of distances, and the distances are not simply longer versions of each other. What limits you changes as they lengthen: a sprint is limited by how hard you can go, and a long-distance race is limited by pacing, fuelling and whether your body tolerates the hours.

• Super-sprint and sprint — Typically a 400m–750m swim, 10–20km bike and 2.5–5km run. The right first race for almost everybody, frequently pool-based, and short enough that the day is about learning transitions and pacing rather than surviving.
• Standard distance — Around 1.5km, 40km and 10km. The classic format and the one most club racing sits at. Long enough to need fuelling and pacing, short enough to train for around a normal job.
• Middle distance — Roughly double the standard distance. The step where nutrition stops being optional and where training time rises sharply — this is where most people discover whether they want the long end of the sport.
• Long distance — Full-distance racing, most of a day. A different sport in practice: the constraints are fuelling, heat, pacing discipline and durability rather than speed, and the training load reshapes a year.
• Draft-legal racing — Where riders may work together on the bike, used in elite and some age-group racing. It changes the tactics completely and makes bike-handling in a group a required skill rather than an optional one.
• Aquabike, duathlon and aquathlon — Two-discipline formats — swim and bike, run and bike, swim and run. Genuinely useful rather than consolation events: they let somebody with an injury or a weak discipline keep racing, and duathlon is published here separately.
• Off-road triathlon — Open-water swim, mountain bike and trail run. A distinct set of skills, a slower and more technical bike leg, and a noticeably different culture from road racing.

The practical advice that falls out of this: start at sprint distance regardless of how fit you are in one discipline, because the thing being learned first is the race itself — the swim start, the two transitions, and running on legs that have just cycled. None of those get easier at longer distances, and all of them are cheaper to learn over an hour than over a day.