Zumba. Zumba began as a mistake: aerobics teacher Beto Perez brought the wrong music to class, then improvised a dance routine to go with it. For his students, it was more fun than work — and it eventually grew into one of the biggest fitness brands in the world. PLUS for our postscript “How You Built That,” how Alex McKenzie is hoping to upgrade the menu of your neighborhood ice cream truck by offering exotic flavors, high fat content, plus low-guilt options for the health-conscious.

One of the most dramatic  stories is that of Josette Tkacik, who three years ago was diagnosed with rheumatoid arthritis (RA), an autoimmune disease that causes intense pain and inflammation of the joints.

The mother of one from Santa Barbara, California, says: ‘I just woke up one morning in such pain that I couldn’t move. My joints were incredibly swollen.

‘I was rushed to hospital and within a week I was diagnosed with severe RA. I was told I’d have to go on medication, but I said no as I was trying for a child.’

Josette, 44, a former dancer with the New York City Ballet, decided to throw herself into exercise.

‘I’d done Zumba before and knew it made me feel good. My husband thought I was insane as I could barely get out of bed.

‘For the first few months, I just moved very gently but then I started to find it easier. Within  18 months, all I had was swelling in my ankles in the morning.

‘I have never taken drugs, and my doctor tells me I am one of a tiny minority to have gone into complete remission without them.

‘I follow a vegan diet, but I am in no doubt that Zumba is what helped me the most.

‘I now teach about 150 students a day, many of them with physical problems. We all have our challenges, but we can use that  to help the next person. Nothing is impossible.

‘Get to a Zumba class, get happy for an hour, and you will be amazed with the changes.’

Josette Tkacik began dancing before she could even walk. Later in life, she studied classical ballet with several notable companies, including The prestigious Joffrey Ballet School in New York and The Metropolitan Ballet of St. Louis, where she was a company dancer. In 2010, a friend suggested she try her first Zumba class. “I remember laughing and being exhausted at the same time. But there was something more….this was a release! This was magic!” Hooked, Josette attended every Zumba class she could find.