Neil Patrick Harris is the Daring Young Man on the Flying Trapeze

Neil Patrick Harris has had a busy summer. Not only is he about to start production on the sixth season of the hit CBS show "How I Met Your Mother," he's currently directing a production of "Rent" at the Hollywood Bowl, starring High School Musical's Vanessa Hudgens and Pussycat Doll Nicole Scherzinger. Harris is also deeply involved in philanthropic efforts, including narrating the Listerine-produced documentary "This Is Your Mouth," which donates $1 per view of thisisyourmouth.com to America's Toothfairy, an organization that helps provide dental care to underprivileged kids.

Keeping in shape is a challenge for everyone with a tight schedule, so That's Fit asked Harris what his secret is to keeping his energy levels high and his body Emmy-worthy. He said, "I take circus classes now and again so I feel like I have some practical strength."

Harris works out at Cirque School in Los Angeles, a studio founded by former Cirque du Soleil aerialist Aloysia Gavre. Using trapeze and floor exercises, instructors create circus circuits. Imagine swinging from a single trapeze for one and a half minutes, doing core strength-training exercises for one and a half minutes, followed by one and a half minutes on the ring. The school offers a variety of ground and aerial classes, focusing on signature Cirque du Soleil moves mixed with Pilates, to increase strength and flexibility.

In addition to flying through the air with the greatest of ease, Harris works out several times a week using the classic combination of strength training and cardio. Flexibility is key to keeping the former Doogie Howser in prime condition.

"I try to concentrate on posture, keeping my body as long as it can be. I've been doing more Pilates and yoga and trying to get into a real cardiovascular routine to increase my flexibility."

Luckily, Harris has a high metabolism, but still has to watch what he eats. "Eating smallish meals more often is best for me," he said. "If I eat a big breakfast, I suffer all day! I'm a grazer."

His weakness? He claims to not have much of a sweet tooth, except for one treat: Reese's Peanut Butter Cups. "When you eat one you automatically have to eat seven, why is that?"

And as for the upcoming sixth season of "How I Met Your Mother," Harris hasn't even seen a script yet, though production starts August 9. "I wish I knew more!" We'll all just have to wait until the premiere on September 20 to find out.

Neil Patrick Harris isn't the only celebrity who works hard to keep their body in top shape. Find out how Valerie Bertinelli stays fit at 50.