After I retired from swimming in 2008, working out wasn’t a top priority in my life. I tried to commit to a gym as soon as I moved back to southern California, but I quickly grew tired of it. Over the next year, after I had part of my collarbone removed, I started feeling gross and unhappy with my body. I knew it was time to get back in the workout routine. But how?

I was doing a charity event in Montana when my friend (and America’s Next Top Model, Cycle 7 winner) CariDee English told me about this kick-ass workout she loved. Now, CariDee is one tough chick, but how hard could a model’s workout really be? She explained it as a combination of ballet, weights and Pilates. Again, I thought, “How hard could that be?” But the results she described were too good to dismiss. This workout targeted all the areas I wanted to improve on: arms, inner thighs, glutes and abs.

The name: Pure Barre.

It was invented in 2001 by a Michigan woman with a business degree and a background in choreography. A decade later, there are 50 franchisees across the country. Pure Barre (pronounced “bar”) is mostly geared toward women, but I heard it would seriously challenge any man.

As soon as I got back from Montana, I searched for the nearest class in my area and started the next day. I have always had a lot of confidence in my athletic abilities, so I was not worried about trying the class. The session was scheduled for 55 minutes. Considering I used to train in the pool for about five hours a day, I didn’t worry.

I should have.

I have never glistened -- girls don’t sweat -- so much in my life. This was literally the hardest workout I have ever done out of the pool. I was almost embarrassed by how poorly I thought I did. I assumed no one in the studio would believe I was a two-time Olympian and gold medalist.

Six months later, the classes are still kicking my butt. But I am definitely seeing results. At least two times a week, I go for an enjoyable beating. I’ve gotten my roommates on board and a few fellow swimmers as well. Some of my male friends have tried it, and they love it too.

“The idea is to get each muscle working to the point of fatigue,” says Chelsea Gregory, who owns two Pure Barre studios in California, “and then we stretch, creating those long lean muscles, without the bulk.”

Pure Barre does not involve any jumping, so your joints won’t get crushed. But there’s a huge cardio benefit.

Here’s just one example: Facing and holding onto the ballet barre, we bring our heels together and keep our toes apart. Rising to our toes, lifting our heels up a few inches, we proceed to bend our knees until our “seat” – the Pure Barre term for “rear” -- comes down toward knee level. (Always keep the back flat and chest up.) From there, we move up and down a few inches, slowly. The burn you get from a simple movement like that is unreal. That’s probably one of the easier thigh exercises, too.

I was also surprised by how challenging the abs section is. During my athletic career, I cranked out a ton of sit-ups and have done a ton of different forms of ab work. But I felt like an ab amateur in this class.

Another example: We use a small five-inch round ball and place it at the small of our backs. We lean back to our lowest point and lift up a small inch and lower back down. Sounds easy, but I promise its not.

It took me some time to get used to the fact that there are not many large movements in this workout. Everything is very small and focused. And tough. But don’t get me wrong – this workout does not crawl by. There is good music and a fast pace. And guys: you don’t need prior dance or ballet experience.

People are often asking me what I do to stay in shape now that my competitive career is over. I think they expect me to say I train for triathlons or marathons, but that isn’t the case. Pure Barre is my main workout. I only swim occasionally. That’s right –- these days my toughest competition comes in the Pure Barre studio.