So you know it involves swim-bike-run but that s about it? The multi-discipline sport of triathlon can often seem complex to the untrained eye. But fear not, with our guide b Emma-Kate Lidbury, you'll soon have a better understanding of the sport that is about to bring more than 4,000 athletes to Blenheim Palace.

There is no doubt about it - triathlon is a kit-heavy sport.

This often deters people from taking it up, but as it grows in popularity, shops such as SBR are offering competitively-priced starter packs which include all the essentials such as a wetsuit, bike, tri suit and run shoes.

On the day of a race, triathletes will pack up all of the kit needed and will set it out in transition (the name given to the area where athletes change from swim to bike and then bike to run) before the race gets under way.

Here, we take a closer look at what is inside the average triathlete s kit bag.

1.BIKE - the bike pictured is a Giant Trinity Alliance Zero, a triathlon-specific bike which is designed with aerodynamics in mind. However, at races such as Blenheim - which are aimed at the first-timer - any bike will do to get you through.

Mountain bikes and hybrid bikes are a common sight, although many competitors will have road bikes. The bike is without doubt the most expensive piece of kit in which a triathlete invests.

Entry level bikes start at about £500 but, at the other end of the scale, it is not hard to spend £3,000 on an all-carbon steed.

2.BIKE HELMET - safety rules mean all competitors have to wear one.

3.SUNGLASSES - contrary to popular belief, these are not worn solely for poser value. On the bike course, many triathletes will clock up speeds in excess of 30mph and if an insect or bit of gravel hits you in the eye at those speeds, it is not going to be pretty 4.BIKE SHOES - lots of first-timers will opt to keep it simple and wear their running shoes on the bike but, for those using clipless pedals, a good pair of bike shoes is essential for faster, more energy-efficient cycling. The shoes pictured are Nike triathlon shoes, which are designed to be easier to get in and out of in transition.

5.SWIMMING HAT AND GOGGLES - the hat keeps your head warm and your hair out of your way so you can cut through the water with less resistance. you won t see much without these.

Some triathletes use regular swimming goggles for open water swimming, but others prefer masks, which can offer better all-round visibility when swimming in lakes 6.WETSUIT AND LUBRICANT- an essential piece of kit for most open-water triathlons in the UK. You certainly wouldn t want to get in the water at Blenheim - where the lake is a chilly 15 to16C at this time of year - without one. But the wetsuit doesn t just keep you warm. Triathlon wetsuits also assist with buoyancy, which means you will naturally have a higher body position in the water when wearing one and should therefore swim faster. Wetsuits are designed to act like a second skin. This means they are tight and can chafe, so lubricating products like Bodyglide ease this. They can also be tricky to get out of quickly in transition so a liberal amount of Bodyglide rubbed around the ankles, knees, shoulders and elbows can help cut transition time.

7.RACE BELT - your race number is attached to this and worn around your waist throughout the race, on your back for the bike and on your front for the run.

8.BOTTLE AND NUTRITION - staying hydrated is important so make sure you have some water or energy drink on the bike and/or the run if you feel it necessary 9.HEART RATE MONITOR - the strap is worn around your chest and the watch worn on your wrist with heart rate readings sent using wireless technology to the watch. This ensures you always know how hard you are working and can monitor your efforts, which is particularly important in a sport like triathlon when racing at too high a heart rate on the bike could spell disaster for the run.

1210 VISOR/HAT - on a hot day, you ll be incredibly grateful for any protection you can get from the sun when you are out on the run.

11. TRISUIT/TRI TOP AND SHORTS - many people often mistakenly think triathletes wear three different outfits for the three different disciplines, but with the clock ticking from the moment you start the swim until the second you cross the finish line, there IS no time for a change of wardrobe. For this reason, you wear one outfit for the entire race which you put on beneath your wetsuit at the start. After the swim, the wetsuit comes off, as do your hat and goggles, but the trisuit (or tri top and bottoms, whichever you prefer to wear) stays on. They are made of hi-tech, quick-drying fabric 12. RUN SHOES with elastic laces - these speed up T2 (the name given to the second transition between bike to run) as it means there are no fiddly laces to get tied up in knots or tangled.