Over the next fortnight 200 plus Britons will take part in two of Europe's largest ski marathons.

The Swedish Vasa Races in Mora (ranging from 30-90km) and the 42km Engadin Ski Marathon near St Moritz, Switzerland. For many it will be the culmination of months of training - running, skiing and rollerskiing - giving them the strength, stamina and technique to complete these long distance challenges. In the UK cross-country skiing is often regarded as 'walking on skis', despite its status as one of the most demanding competitive sports.

The emergence in popularity of ski marathons reflects a growing trend for sporting challenges among the UK's growing tribe of endurance athletes: triathletes, rowers, mountain bikers, adventure racers and others often convert easily to cross-country ski racing.

Snowsport England Nordic Development Officer Iain Ballentine explains the appeal: 'Ski marathon racing is in many ways the ultimate racing experience. You get the endorphin rush as you race up the hills - all major muscles engaged - with the adrenalin rush of speeding downhill through forest trails, and competing against thousands. Add to that hugely supportive crowds, breathtaking scenery and pure mountain air, and you have a pretty special event'.

12,000 skiers take part in the Engadin Ski Marathon in Switzerland each year, making it one of the largest cross-country ski marathons in the world, and the most popular with British skiers. This year will see almost 140 Brits take part in the race, with serious ski racers, such as the team from the Manchester Cross-Country Ski Club, racing alongside more leisurely competitors, such as 16 racers from the London law firm Freshfields.

The nature of the sport is such that you can be really serious about your racing and training, or just ski along with friends and take in the views. The Vasaloppet in Sweden is the main event in a week of ski racing. A 90km race, it is one of Sweden's biggest sporting events with 14,000 competitors and a huge TV audience. Since it began in 1922, 404,545 sportsmen and women have completed the race. Shorter races exist for less experienced skiers, with a half distance race and a 30km 'Short Vasa' race aimed at families, with a minimum competitor age of 12.

Across Europe there are many smaller ski marathons, typically with fields of several hundred and organised by resorts to attract tourists to the area. (For a race calendar see www.rollerski.co.uk/nf003.html ) Cross-country skiing is a surprisingly straightforward sport to become involved in.

Many different holiday companies offer trips, some with leaders or instructors to teach you the basics, and some culminating in a ski race. Many major alpine resorts have Nordic ski schools and ski hire, and Snowsport England, the governing body of the sport in the UK, runs its own open training camps for aspirant racers.

The cross-country ski racing season not over yet - the last major ski marathon is the 38k 'Skarverennet' in Geilo, Norway on 22nd April. But 2008 ski racers can start their training now, and carry on through the summer. In the UK, you can train for cross-country skiing on rollerskis, which gives almost exactly the same feeling as cross-country skiing on snow, but with wheels. Nordic ski clubs across the country do courses and training sessions, and more information can be obtained from England's Nordic website. The Rollerski Co in London and Windsor, also offers rollerski courses and instruction for individuals and groups (including schools).

Whatever your age, level of fitness or experience on snow, cross-country skiing offers a world of sporting opportunity, and a friendly community of clubs and instructors is ready to help you get started.