It was 1989 in Santa Monica. Duran Duran, Roxette and Bon Jovi blasted from the radio, while Madonna implored fans to express themselves. The fashion-conscious wore leopard print, shoulder pads and plaid. The body-conscious headed to Johnny G's Spin centre to burn off 600 calories an hour. Born in South Africa, Johnny Goldberg had moved to the US a decade earlier, working as a personal trainer and taking part in a host of endurance cycle races. One night, while out training on his bike, a passing car narrowly missed him. It was then he had the idea of taking cycling indoors. Spinning was born.
Goldberg devised a programme of classes based around a specially designed stationary bike. Using a mass braked flywheel – essentially a big, stationary cog – he was able to recreate actual road conditions. Soon after opening that first Santa Monica studio Johnny G, as he came to be known, had won a loyal following among the city's cycle enthusiasts. In 1991, he took his classes to Hollywood and by 1994 he had patented the Spinning logo and opened Johnny G's Spinning Headquarters in Culver City, LA. Classes have evolved from a collection of punters cycling along to some background music to full-on sporting experiences.
Hill climbs, sprints, jumps and downhill freewheeling are simulated; instructors encourage their audience to visualise outdoor environments. The past decade has seen a new strain of realism take hold: so-called "terrain-based" classes, simulating race conditions complete with wind and resistance, have become more popular. While you'd be hard-pressed to find a pro-rider joining the amateurs in their training, it's all based on the same principles racers use. "I use home trainers a considerable amount," explains Tom Southam, who races for the Rapha Condor Sharp team. "Most obviously when the conditions outside make it difficult or impossible to go outdoors."
Classes work muscles in ways not offered by other cardiovascular activities, strengthening the core, back and shoulders while working out the quadriceps and hamstrings.
No wonder spinning zoomed out of California and conquered the fitness world. You'd be hard pressed to find a gym in the UK that doesn't offer some kind of cycling-based class. The studios are packed with punters eager to nab one of the stationary bikes. Almost all follow more or less the same formula. Groups are shown how to sit on their bike, how to judge what height to set their seat at, and how to hold their handlebars – and then they're off with a warm-up, as the music – which can incorporate anything from African drum rhythms to the latest chart hits – gradually builds. The main body of a class revolves around intervals – bursts of energetic cycling, frequently at a higher intensity – interspersed with freewheeling downhill segments to give the muscles a break. At the end, there's the cool down, the stretching and the deep breaths. Breathing is important – that and drinking water. You're reminded of both, frequently, throughout.
In an age of short-lived fitness fads this format has proved remarkably durable. Every year more snappily titled classes jostle for attention (Jukari! Stomp! Krump!) but spin remains the most crowded class on offer, drawing die-hard devotees and occasional visitors alike.
"I've been doing it for years," says Sophie Butcher. "In the first few you sweat so much but if your instructor makes it good fun you get over the pain. I go to a class lasting an hour an a half. It's always packed."
"Spin is our bread-and-butter studio class," agrees Tim Foster, head of fitness experience at Virgin Active. "It has always been the most popular."
Foster points to a variety of factors in explaining the workout's success: it's relatively straightforward (there's no need for complicated routines or advanced co-ordination); by using a series of dials on their bike, spinners can control the intensity of their own workout; the instructors' approach varies from one to the other, so there's an element of variety. With spinning on offer since they opened in 1999, Virgin was one of the first gyms in the UK to boast dedicated studios equipped with fixed bikes. "It united our customers. A lot of classes tend to be male- or female-dominated. Spin is equally popular with both sexes."
Johnny G, has been developing a new idea too: kranking. Essentially a spinning class for the arms, kranking involves sitting on a sort of bicycle, feet on the ground, arms in a pair of handle-bar height "pedals". It promises to whip the upper arms into shape, banishing bingo wings in its wake.
From its origins as a fitness fanatic's personal training scheme to global domination, spinning shows little sign of slowing down. Julia Roberts is said to be a fan, while Kranking has won fans in Jennifer Lopez, Bruce Willis and Hugh Jackman.
As for what's next, we can only guess. Underwater spinning, perhaps? No – that's already been done...