The race
A triathlon comprises a swim, a bike and a run, usually in that order. The swim often takes place in a lake, sea, or other open water; the bike and run will generally be on road and pavement.
Super sprint A 400m swim, 10km cycle and 2.5km run. The most accessible race for novices.
Sprint 750m swim, 20km cycle, 5km run. An increasingly popular distance for amateur triathletes.
Olympic distance 1.5km swim, 40km cycle, 10km run. Also known as 'short course', and the format raced in World Cups, too.
Middle 1.9km swim, 90km cycle, 21.1km run. This distance, also known as 'Half Ironman', now has a pro circuit and world championships.
Full distance or Ironman 3.8km swim, 180km cycle, 42.2km run. For those fond of hallucinations and uncontrollable tears.
Deca Triathlon Ten times the Ironman distance. Allow a fortnight for the whole thing. Masochists only need apply: Cornishman Bob Brown ingested 95 painkillers in the final days of the 1997 race and took nearly two years to recover.
The jargon explained
Aerobars A set of bicycle handlebars that get you low and aerodynamic.
Age-grouper Anyone who races triathlon but doesn't train professionally. Most events break down into five-year categories.
Biking Never 'cycling'.
Bonking When your body runs out of energy (avoided by taking on glucose).
Brick training Combining two of the three disciplines in training, usually biking followed by running.
T1 and T2 The transition areas where you change from swim to bike and bike to run respectively. Normally on the same square plot of grass.
Tapering To maximise all that training, you need to rest. In the last week or two before the big day, cut down the exercise, so your mind and body are raring to go by the start.
Swim
'The front crawl may be the quickest,' says triathlon coach Mark Kleanthous, 'but there's no problems at all with doing breaststroke. Some athletes have even completed the Ironman swim doing backstroke.' (Backstroke is banned at some triathlons, including London, to avoid confusion between an athlete backstroking and one who is on the verge of drowning.)
The swim takes up only 15-18 per cent of the race. And because you'll gain such high fitness levels through cycling and running, you can focus on technique. Each swim session should include drills that break down the parts of the stroke - arm action, leg action, breathing, body balance and timing - before you bring it all together.
How much should you swim? Elite athlete Richard Stannard recommends a little and often (three times a week for 30-40 minutes each time). If your event includes an open-water swim, practise in your wetsuit in open water.
The gear
The kit you need and the price to pay (excluding blood, sweat and tears)
Wetsuit
A good wetsuit will be comfortable, flexible, and provide insulation and buoyancy.
Top end: Orca Apex 2 £350 orca.com.Uniquely, it has little pockets of air trapped in the neoprene to help your buoyancy. Worn by Tim Don.
Entry level: Foor Quantum £125. triuk.com
The neoprene is coated with a 100 per cent smooth skin finish, to help you slip through the water.
Googles
Top end: Zoggs Predator Mask £16.99 zoggs.com. The scuba-style mask comes into its own in open water, as they won't get knocked off or leak.
Entry level: Aqua Sphere Mako £6.99. swimshop4u.co.uk. Easy-adjust buckles, cosy fit and excellent UV protection.
Bike
The bike leg isn't only the longest of the three disciplines (taking up about 50 per cent of your race time), it's also the one where you must integrate your body with a machine. So it's important your bike is right for you - and that you are positioned correctly on it.
The key to a good set-up, says Phil Cavell - a specialist in cycling ergonomics and the founder of the London bike centre CycleFit - is getting the correct saddle height (which is the distance from the pedal axle to the top of the seat). Cavell says: 'Your saddle height should be set so your legs are almost fully extended - about a 30 degree kink in the knee - at the bottom of the pedal stroke.'
Either a mountain bike or a cheap road bike will be fine for triathlon. Regular triathletes will probably want to upgrade to carbon wheels, helmets shaped like teardrops or special lightweight bike frames. The rule is: the lighter the bike, the more it will cost.
Make sure you have a helmet that adheres to the necessary safety standards - you can't race without one. It's also worth buying a pair of cycling shorts or by the end of the bike your backside can feel like it has been through a cheese grater. Don't worry about clipless pedals unless you're already a confident cyclist.
As for physical training, one long ride a week (at least an hour) is vital to improve fitness and endurance. You can supplement this by commuting. 'And if it's a long way to work, you can always cycle in and get a lift home,' says triathlete Mark Kleanthous. Keep your bike clean; check tyre pressure regularly; and it's worth learning how to mend a puncture, too.
Bike
Speed and weight are vital.
Top end: Cervelo P3C £4,435 ultimatepursuits.co.uk. The carbon-framed P3C has 19 Ironman victories to its credit.
Entry level: Claud Butler San Remo £299.99. falconcycles.co.uk. Ideal for novices.
Helmet
No helmet, no race. Make sure its comfort matches its strength.
Top end: Met PAC VII £124.99 fisheroutdoor.co.uk. Ultra hi-tech design.
Entry level: Giro Stylus £39.99. ultimatepursuits.co.uk. A lightweight, comfortable lid.
Shoes
The so-called 'clipless shoes' actually lock on to the bike pedals.
Top end: Shimano TR50 £109.95. ultimatepursuits.co.uk. The single strap saves time in transition; ventilation is good, so your feet shouldn't smell like death.
Entry level: Exustar SR900 £49.99. rsi-cycles.com. Light and won't break the bank.
Run
'Good-fitting shoes are essential,' says Britain's 2006 world champion Tim Don. 'You should get your running style analysed by a professional, who can then prescribe the right ones for you.' Brick training - training in two disciplines consecutively, for example a bike ride followed by a run - is vital, says Don. 'You have to run after jumping off a bike in triathlon, so mimic that sensation in practice.' Regular cycling followed by a period of running should lessen the jelly-leg feeling.
The gear
Tri-suit
Comes in one- or two-piece; can be worn for entire race.
Top end: Skinfit Speedsuit II £110 skinfit.uk.com. Very close-fitting suit. Especially good for pool-based triathlons.
Entry level:Craft Women's Tri Race £59.99. craft.se. Breathable and ultra-light.
Shoes
Top end: Brooks Trance 7 £110. brooksrunning.co.uk. A balance of control, cushioning and feel.
Entry level: New Balance M755SR £60. newbalance.co.uk. Good value and still very respectable.
Common errors and how to avoid them
Last October, 30-year-old Chrissie Wellington, from Suffolk, became the first Briton to win Ironman Hawaii - in only her second Ironman. She had been a pro for just 10 months. Here is her advice for how to beat the five typical triathlon problems.
1 Losing motivation
The main reason we wander from our goals is relying on only ourselves for motivation. Joining a club is well worth it: there are more than 100 up and down the country and it's a great way to make friends, find training partners and pick up tips. Don't be nervous if you've never swum, biked or run before: most cater for novices.
2 Wasting money
Buy or borrow the essentials: you don't need fancy gadgets or kit. I won the World Age Group Triathlon Champs in 2006 using a borrowed wetsuit and third-hand bike!
3 Running out of juice
If a training session or race is longer than an hour, you'll need to take in simple sugars, via an energy drink, a gel or my choice - malt loaf and jelly babies. Don't risk an upset stomach by trying new products on race day.
4 Being taken by surprise
Recce the course beforehand, even if it is just involves analysing the course profile on the web. You don't want to hit the bike come race day and be faced with a mountain when you've only cycled on the flat.
5 Tough transitions
Transitions are important, particularly in the shorter races, so practise them: including getting your wetsuit on and off at speed. I use a non-petroleum-based lubricant around the ankles - not Vaseline, which eats the rubber - and put the lube on with a rubber glove to stop my hands getting greasy (it does attract a few weird glances).
Great triathlons of the world
Escape from Alcatraz Triathlon, San Francisco
8 June
A non-standard 1.5-mile swim, 18-mile bike and 8-mile run. Freezing-cold waters, dangerous currents, 18 miles of hilly biking and a run that includes the infamous Sand Ladder - 400 steps up a cliff - mean that the event is as tough as the prison. escapefromalcatraztriathlon.com
Noosa Festival, Queensland, Australia
11 October
Various distances, Noosa, on the Sunshine Coast two hours' drive from Brisbane, stages a five-day celebration of endurance sport that has thousands of everyday Aussies rubbing shoulders with famous international athletes such as Grant Hackett, Kieren Perkins and Robbie McEwen. The main event is the triathlon. usmevents.com.au
Ironman Hawaii, Kona, Hawaii
29 October to 2 November
Full distance Ironman. The first event in 1978 attracted 15 athletes. Thirty years later, to secure a place among the starting 1,800, you must qualify at one of the 21 global events or strike lucky in a lottery. Lava fields and the Pacific provide a mystical backdrop. ironmanlive.com
· It's three months to the Mazda London Triathlon on 9-10 August and you will actually enjoy it if you follow triathlon coach Joe Beer's 12-week training programme.
