We all look to celebrities for fitness inspiration, but the reality is that behind pretty much every enviable celebrity body, there’s a trainer making that progress happen. For celebs like Shakira, Kelly Ripa, and Karlie Kloss, that trainer is Anna Kaiser.

Kaiser is no stranger to the fitness world. She started teaching dance classes in 1997, when she was still in high school, went on to study dance at the University of California, then kinesiology, sports medicine, and functional anatomy at Mount Sinai Medical Center. Thanks to her combination of knowledge about how the body moves and how the body works, her high-energy circuit training, HIIT, dance, Pilates, and yoga workouts get the job done—and people took notice of the results of her training methods early on.

By word of mouth, Kaiser became a go-to trainer for celebrities striving to look better and reach a higher level of fitness. Now, she has her own program, AKT, that includes both online-based fitness programs and studio locations at which anyone can get the same training that keeps their favorite celebrities in top shape.

We caught up—and worked out—with Kaiser to find out just how she and her celebrity clients maintain their enviably fit physiques.

Kaiser’s wearing: Old Navy Active Semi-Fitted Run Shorts ($16.99, oldnavy.com); Loose-Fit Performance Bomber Jacket ($44.99, oldnavy.com); Seamless Light Support Sports Bra (she layered two of them) ($19.99, oldnavy.com)

Check out the rest of the Old Navy Active collection at oldnavy.com.