Strong by Zumba is not a dance class, it's a high-intensity exercise routine that is unlike anything Zumba Fitness has ever offered. The company's first entirely new workout program debuted just one year ago. Now, between 200,000 to 300,000 people attend classes each week.

That's a lot faster than the original program took off: Zumba first launched in 1999, and it took the company six years to reach 300,000 students per week, says Alberto Perlman, Zumba Fitness's co-founder and CEO. Perlman calls Strong by Zumba's growth unbelievable. "We have never seen a response to anything we have ever launched that was this big," Perlman says.

Strong by Zumba pairs certain exercise moves to music, but it's not choreography. The company worked with DJs like Timbaland to ensure that every squat or lunge matches a sound in a song. The idea came about after Perlman and co-founder Alberto Perez attended several high-intensity workout classes but left feeling frustrated.

"There was no connection between what the instructors were doing in the class and the music they are playing," Perlman says. "The most motivating part of fitness is the music."

Over the last several years, Zumba has released similar programs based on the original workout, like Aqua Zumba or Zumba Kids. But Strong has already taken off; it's being taught in 100 of the 186 countries where Zumba is offered (the company's programs aren't allowed in embargoed countries like Cuba, North Korea, and Iran, where six young people were arrested in early August for promoting the dancing exercises).

High-intensity workouts have become very popular recently, especially at boutique fitness centers. But Perlman argues that these programs are too expensive for most people. Strong by Zumba is much more affordable, he says, adding that prices can range depending on the instructor or location. In some cases, prices could go as low as $5.

Zumba, which was Inc.'s company of the year in 2012, collects fees from instructors, which can range between $250 and $300. It also requires teachers to pay a monthly rate that gives them access to company benefits like educational videos. Zumba instructors find places to teach, whether that's at a gym or in a church basement, which can also dictate the price of a class.

Perlman says Zumba Fitness has 250 employees but wouldn't say how many instructors were currently working for the company. In 2012, when Inc. profiled Zumba Fitness, the company had a reported valuation of more than $500 million. Perlman says the company hasn't raised any additional money since then and are currently profitable, but wouldn't disclose revenue figures. Zumba Fitness also makes money from its retail arm: Inc. reported that the company expected to sell 3.5 million units in 2012.

"When doing innovation, don't look at what other people are doing, focus on the customer," Perlman says. "The ones that work are the ones that are completely customer-centric."