On a sunny afternoon in a gym in Kensington, the yoga matts are vibrating to the sort of beats that you'd more usually expect to hear a nightclub in Brixton. An instructor is teaching a class - mainly made up of white, middle-class women - a Jamaican dance move called the “dutty wine”. It involves a serpentine wind of the bottom - or booty as we’re calling it today - while the knees and neck rotate wildly. The effect is supposed to be a powerful physical booty call. Unfortunately, I feel more like an embarrassing relative getting “illegally funky” at a wedding.

This is the Nike Rockstar Workout Dancehall: the latest in themed dance classes to arrive in Britain from America. The routines were devised by choreographer Jamie King, famous for working with Madonna, Christina and Britney, who realised that there was a market for women eager to imitate the style of dancing you see in an MTV video. His first routine, the Rockstar, hit Britain in 2005 and was based around hairbrush-as-a-microphone fantasies, with air-guitar windmills and scissor kicks. Dancehall, though, is edgier and, in MTV-speak, more “dirrty”. It has just been rolled out at 50 gyms nationwide, bringing underground Caribbean “riddims” to such unlikely venues as Virgin Active gyms, The Third Space and JJB.

Carl McCartney, National Group Exercise Manager for Virgin Active, explains: "The workout was developed to respond to the latest moves on the music scene. It’s a fitness routine that combines the latest choreography with music that can make you feel really motivated."

Even so, it has to be said that dancehall is an unlikely contender for a coporate-sponsored fitness class. The genre, also known as ragga, has become impossible to talk about without mentioning the homophobic violence that has led to the nickname, “murder music”. The most infamous dancehall track, Boom Bye Bye by Buju Banton, advocates the execution of gay men, while today's soundtrack features tracks by Elephant Man, who was dropped from the Mobo Awards in 2004 for refusing to apologise for his homophobic lyrics. Female ragga stars, such as Lady Saw, have found themselves on the wrong side of obscenity laws in Jamaica for their overtly sexual dancing. If you don’t know your patois from your patios, it can all seem rather rather alarming.

“Most people do find the workout rather embarrassing to begin with,” admits McCartney, who says the more graphic elements of dancehall have been toned down. “I wouldn’t say the music is intimidating, but some of the moves can make you feel self-conscious.”

Among them are the “bogle”, a squat move named after the leading dancehall choreographer Gerald "Bogle" Levy, who was murdered in 2005, and the “pon de river”, a snake-hipped leg kick. Even aside from the booty wiggles, though, this is not a class for the faint-hearted. After 45 minutes, the instructors have impressive sweat patches, while some press-up have left me feeling as though my arms are strung with piano wire.

“It hits your arms, lower abdominals and legs,” says McCartney. “Because of the rotations involved, you’re using the muscles around your stomach to trim the waist, and in your thighs to tone your hips and butt.”

While it’s unlikely that dancehall will ever become as ubiquitous as salsa lessons, the class is already encouraging aspiring “laydeez” to sign up. Says Laura Hind, another dancehall first-timer, “I chose the class because I’m hoping it will boost my confidence on the dancefloor. My ultimate aim being to demonstrate the whole routine start to finish in a club.” Personally, I’m keeping my own moves behind closed doors for now. I’m not ready for anyone to ogle at my bogle yet.

For more information on the Nike Rockstar Workout Dancehall, visit www.virginactive.co.uk .

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