The Workout That Gives Britney Spears Her Sexy, Sculpted Legs

britney-spears-workout
Britney Spears Courtesy of Britney Spears/Instagram

Britney Spears loves to post her complicated workout routines on Instagram, but one of her fitness tricks is surprisingly simple: running.

After the Piece of Me singer, who is dating fitness model and Slumber Party music video costar Sam Asghari, popped into Equinox’s Precision Running class at Westlake Village, California, recently, Us reached out to the pro who designed the method to find out why it’s such an effective total body toner. According to David Siik (who taught the June class the Grammy winner popped in on!), the treadmill workout is based on high intensity interval training and incorporates a combination of speed and hill intervals.

“The treadmill is a marvelous machine that has the ability to micro-program our cardio in a way that is so exact,” the celebrity trainer, who created Precision Running four years ago, tells Us Weekly. “This class creates a track and field experience on a treadmill.”

The performance-based class, which counts Tom Brady, Renee Zellweger and Shay Mitchell as fans, begins with a warm-up, then is broken down into two to three interval segments totaling 38 minutes of non-stop running, which can be speed or incline-centric, followed by a cool down. “It brings the athlete back out of a person, even if they’ve never been an athlete,” Siik says. “But the ultimate goal is making running accessible.”

Siik notes running is uniquely effective because it increases calorie burn and muscle. “No. 1, it’s an impact sport. That’s the biggest difference when you talk about it compared to swimming or cycling or the other kind of cardio things that we do,” Siik explains. “It requires an immense amount of energy to lift your foot off the ground. Each time you have to fight gravity and that’s the biggest thing about running compared to a lot of non-impact sports — you have to fight gravity back. To push yourself vertically up while you’re going fast. It requires so much energy to do that.”

And while running may be thought of as mostly a leg workout, Siik says, it’s “truly a full body exercise. The chain reaction from your head to your toes every time you change your pace or you all of a sudden have a hill causes hundreds of calculations. Your brain has to make so many quick changes that engage all of these different muscles in your body, for example, to tilt your pelvis, to have your chin a certain way, your arm drive, all these things and the constant core work, that’s one of the enormous benefits other than just a really big calorie burn.”

Body benefits aside, the 45 or 60-minute class is also popular among Equinox members like Spears because “it’s fun and it’s engaging and it’s very self challenging,” Siik says. “But also you’re able to do it often — two to three days a week — and the next day you’re not going to be so sore that you can’t walk.”
Siik credits the celeb following that Precision Running has created over the years to the fact that “it’s so time efficient for them. Many people think ‘Wow, they’re so beautiful and they have such awesome physiques,’” he opines of actors. “But they work hard. We saw it with Britney — she definitely enjoyed the class and the benefits. She’s a great runner.”

Sign up now for the Us Weekly newsletter to get breaking celebrity news, hot pics and more delivered straight to your inbox!