Fitness crazes are almost always fads, but Zumba is the rare exception. Eighteen years after it exploded into being, and five years after being named Inc.'s Company of the Year for 2012, the Latin-dance-party-inspired fitness brand is still going strong. As a matter of fact, "Strong by Zumba," the company's new class, is growing even faster than the original one did when it first arrived, says CEO Alberto Perlman. Below, Perlman reveals what he and his two co-founders--all named Alberto, weirdly enough--have learned over the course of their surprisingly durable success story.  

Inc.: Your background is in technology, but in 2001 you teamed up with a fitness instructor, Alberto "Beto" Perez. How do you tell an idea that's crazy from one that's just out of the ordinary?

Perlman: Zumba was already happening, but at a very small scale. It wasn't totally out of left field. You have to always be listening. When you find something that's hyperlocal but you're seeing a bit of a fever around it, there's an opportunity there.

How hard was it to convince other people that this was a solid idea?

Early on, I was pitching the CEO of an infomercial company. He said, "This is cool, but does Beto speak English?" So I called and asked him. He said, "Dígale que sí"--"Tell them yes." For the next 60 days, we tried to teach Beto English. It wouldn't sink in. So on day 58, he says, "Just teach me how to say, 'Nice to meet you. Sorry, I need to go.' " The guys from the company came to watch him teach a class. Beto comes off the stage and says, "Nice to meet you. Sorry, I need to go." Then he runs off and hides in his car.

Zumba charges instructors for licensing and teaching materials, but decided not to charge gyms or participants. When should you leave money on the table?

We reached that decision in service of making the instructors successful. We said they should be able to teach anywhere--why limit them? There was a conflict between taking more money and reaching more people. We chose reach, because we want everyone to be happy and fit. The answer is look at your mission. The brand has the answer. Ask the brand.

Zumba's instructors are its customers, and their passion has made the brand a global phenomenon. How do you create an audience that evangelizes for you? 

You don't. They have to want to do it. Invest in making your product authentic and something that people are going to want to share. Then you give them more tools and more outlets, and you celebrate the ones who do it.