Duathlon and aquathlon: distances, rules and London races

A duathlon is a run, a bike ride and a second run. Under British Triathlon rules the sprint duathlon is 5 km, 20 km and 2.5 km, and the standard is 10 km, 40 km and 5 km. An aquathlon is a swim followed by a run; the sprint aquathlon is a 500 m swim and a 2.5 km run.

This guide sets out the official duathlon and aquathlon distances and minimum ages, explains who each format suits, and lists the races near London whose details we could check on the organisers' own pages.

Duathlon distances

The table comes from Appendix A of the British Triathlon Competition Rules 2026 (April 2026 version). The minimum age is your age on 31 December of the race year. Miles are rounded.

Notice that the second run is shorter than the first at sprint and standard distance. The sprint duathlon has the same 20 km bike as a sprint triathlon, and the standard duathlon has the same 40 km bike as an Olympic triathlon. The run you do before the bike replaces the swim.

Races abroad held under World Triathlon rules use the same sprint and standard distances but set the minimum age at 16 for sprint and 18 for standard. Organisers in the UK also adjust courses to their venue, so the distances on an entry page may differ a little from the table.

Aquathlon distances

British Triathlon's Appendix A lists a sprint aquathlon of a 500 m swim and a 2.5 km run (0.3 miles and 1.6 miles), with a minimum age of 15. We have not confirmed the other aquathlon rows in the rules, so for longer aquathlons, check the organiser's website for the swim and run distances and the age limits.

An aquathlon has one transition. You come out of the water, take off your wetsuit if you wore one, put on running shoes and go. In open water the same wetsuit temperature rules apply as in a triathlon: for swims up to 1500 m, a wetsuit is mandatory below 15.9 °C and forbidden above 22 °C if you are 59 or younger (above 24.6 °C if you are 60 or older).

Who duathlon suits

A duathlon keeps the bike and the transitions of a triathlon but leaves out the swim. That makes it a good fit in several situations.

• Runners who want to try multisport. If you already run 5 km comfortably and own a bike, a sprint duathlon is a short step.
• People who are not yet confident swimmers. You can race now and work on your swimming for a triathlon later.
• Triathletes out of season. A duathlon does not depend on water temperature, so it can be held in the colder months. The Dorney Lake Duathlon in November is an example.
• Anyone practising transitions. Two transitions in a short race are useful practice for T1 and T2 (the changeovers between sports) before a triathlon.

The hard part of a duathlon is the second run. Your legs are already tired from the first run and the bike, and the change from cycling to running feels heavy at first. Brick sessions, a ride followed straight away by a run, are the best way to prepare for that feeling. Our brick workout guide explains how to build one into your week. For safe places to ride, see our guide to cycling training in London.

Who aquathlon suits

• Swimmers and runners without a racing bike. You need very little kit: a swimsuit or tri suit, goggles and running shoes, plus a wetsuit if the water is cold.
• Young athletes. Some clubs run aquathlons for juniors. Thames Turbo Triathlon Club ran a Junior Aquathlon in 2026.
• Triathletes working on the swim. An aquathlon is a race-day test of your open-water swimming and the switch to running, without a long bike in between.

If the aquathlon you choose has an open-water swim, practise first at a supervised venue. Our guide to open-water swimming in London lists places with organised sessions. Never practise in the Thames, canals or docks outside an organised session.

Duathlon and aquathlon races near London

We list only what we could check on organisers' own pages, on 6 October 2026. Dates that have passed are marked as past.

Dorney Lake Duathlon

Dorney Lake, also known as Eton Dorney, is a rowing lake near Windsor. RunThrough's Dorney Lake venue page lists only duathlons for that venue, and the next one shown when we checked was the Dorney Lake Duathlon on 8 November 2026. RunThrough's page is the place to check distances, start times and entry details. Other organisers also hold events at Dorney Lake, but we could not confirm their dates on official pages.

Thames Turbo aquathlons

Thames Turbo Triathlon Club, which also runs the Thames Turbo Sprint Triathlon from Hampton Open Air Pool, held a Junior Aquathlon on 7 June 2026 and a Women's Aquathlon on 20 September 2026. Both have passed. The club's races page did not give distances for these events in the details we checked, and 2027 dates had not been published, so watch that page for next year.

London Duathlon (Richmond Park)

The London Duathlon in Richmond Park is a well-known name, but we could not find a confirmed date for a future edition. The event's own website did not load when we checked, and the only live page we found was a charity entry page. We do not list it as a current race until the organiser confirms a date. If you are interested, check the charity's page and look for an official announcement.

Aquabike: the other two-sport format

You may also see aquabike on entry pages: a swim followed by a bike ride, with no run. It suits people who cannot run because of injury or who prefer to avoid it. In the UK, Outlaw Triathlon's Nottingham weekend on 22 and 23 May 2027 includes an aquabike alongside its half-distance race. Distances vary, so check the organiser's page.

Getting started

For a first duathlon, you need a roadworthy bike, a helmet, running shoes and clothes you can both ride and run in. Train two or three times a week across running and cycling, with an occasional brick session, and build up gradually. For a first aquathlon, focus on continuous swimming and on running straight after you get out of the water.

When you are ready to add the third sport, our sprint triathlon guide explains the next step, and the guide to triathlon distances shows how all the formats compare. If you have a medical condition or have been inactive, see your GP before starting hard training.

Frequently asked questions