The energetic South American dance workout Zumba is taking the US by storm – and now it's over here. Alice-Azania Jarvis takes to the floor

At the Virgin Active gym in London's Broadgate, 30-odd women are being taught to shimmy. "Arriba!" ("Upwards!") squeals Margarete, undeterred by the stiffness of her students' efforts as, with varying degrees of success, they do their best to co-ordinate jiggling arms with an on-the-spot samba.

Naturally, I'm tending towards the incompetent end of the scale – though perhaps not quite as unswervingly as I could be. I've tried Zumba classes before – twice – but in an entirely different setting. Then, I was standing at the back of a class of 50-odd others, in a sweaty, wood- panelled hall in Little Havana, Miami. The class whooped and clapped like something out of Fame (were Fame to be set in Florida and scripted in Spanish). At regular intervals, volunteers would get up onto the mini-stage and dance alongside the instructor. This, one of my fellow dancers told me, was what the class was all about: excitement, participation and genuine fun.

In the United States, Zumba Fitness has been a phenomenon for some time. It is the country's fastest-growing fitness trend, after launching nine years ago and spawning more than 20,000 instructors. It has just been incorporated into Michelle Obama's Get Moving campaign and, later this year, a giant Zumba class is to be given on the White House lawn.

Not bad going, given the workout's humble origins. Its founder, Beto Perez, was raised in Colombia by his single mother and arrived in the US in 1999, with little money and no English. He had been teaching his innovative classes for two years at local gyms when his potential was spotted by Alberto Perlman, who offered to invest. The pair produced a single low-budget infomercial, and before long had landed a promotion deal with Kellogg's. From 2004 they began to expand internationally, and have since launched a host of spin-offs: clothing lines, aqua-aerobics classes and specialised classes for children and the over-fifties.

Back in Britain, looking around at my fellow Virgin Active classmates, it's clear the workout's success is, in large part, due to its sheer enjoyability. Ten minutes into the class, and everyone (myself included) is sporting a Cheshire-cat-sized grin. It's hard not to: the soundtrack (a heady mix of Latin, African and pop beats put together in-house by Zumba Fitness' own music producer) is disarmingly infectious, and our instructor, Margarete, is practically bursting with enthusiasm. Challenging as some of the routines may be, they are not intimidatingly so.

Even I – fundamentally lacking in co-ordination – can see the improvement in my technique over three sessions. I may not be giving Shakira, one of Beto's various celebrity devotees, a run for her money (yet), but I'm certainly picking things up. Indeed – and in contrast to many a fitness franchise – this inclusivity forms a central part of the company's ethos. Although the steps can be complicated, the routines aren't.

Becoming an instructor requires little in the way of financial investment. Beyond the initial outlay for the training sessions and the CDs, instructors are recommended, but not coerced, into joining the Zumba Instructor Network. Further investment is entirely voluntary. The upshot seems to be that instructors ooze enthusiasm as they work, and their students aren't left feeling discouraged by lack of progress. It's an assessment Margerete agrees with. "I get a lot of people who have gone to dance classes and found them too intimidating. It takes a long time to pick up a routine, and sometimes they need partners. With the Zumba workout, you see people go from being worried that they might not be able to keep up, to just relaxing and having fun."

Of course, the feel-good factor isn't the only draw for the crowd here. By the final third of the class, we're all panting and shiny with sweat. A Zumba class, says its creators, provides an effective form of interval training, alternating as it does between rapid cardio-heavy routines, and gentler toning styles. Participants can burn between 600 and 1,000 calories an hour, depending on how vigorously they follow the routine.

"We first saw Zumba when visiting the US at a fitness convention, and witnessed first-hand the energy and excitement that the programme brought," explains Carl McCartney, Virgin Active's national group exercise manager. "We felt that our members would benefit both from the workout and from the adrenaline highs that the class brings." Certainly, when I awake the day after my workout, muscles I hadn't known existed ache. Best of all, I can feel the effects around my torso – an area hitherto resistant to my (frequent) toning attempts.

Enjoyable and effective – it's a combination that has set the brand on a path to success right across the globe. More than 6 million people regularly participate in Zumba classes in some 75 countries. Around 2,200 enthusiasts attended last year's instructor convention – footage shows them leaping around, Southern Baptist style, while Beto preaches the gospel – and 3,500 are expected at this year's event in Orlando, Florida.

Curiously, nowhere has embraced the workout more than northern Europe, so much so that in the Netherlands some 40 incidents are reported each week of the brand's name being used to attract punters under false pretences. Fans cite the sunny escapism offered by the class as an incentive to work out, despite grey European skies and chilly temperatures.

All of which, then, bodes well for the UK. Zumba became available at Virgin Active in January – and has become one of the chain's most popular classes, with waiting lists forming for the 164 classes on offer. News that Perez is soon to visit the UK in person has only boosted to semi-rel-igious fervour of the workout's devotees. Corny as the company's slogan – "Join the party!" – may be, it has to be said: the offer isn't unappealing.