Faith Hill's 41st birthday present to herself: a bikini photo shoot! The svelte country superstar graces the cover of December's Shape magazine, showing off her toned tummy. She says it's Pilates that has helped her reach her fitness goals.

"I could bend in ways I haven't been able to since I was a teenager," she tells the magazine of the benefits of Pilates. "My husband loves it!"

Hill admits it took years for her to settle on a workout routine.

"In my 20s and 30s, I'd go through phases with exercise, working out for four weeks before a big tour or video shoot and not doing much afterward," she admits. "Then I had three kids and turned 40, so I decided to make a lifestyle change."

Hill and hubby Tim McGraw keep each other motivated with joint workouts that include four miles on the elliptical machine, weight lifting, sit-ups and push-ups. Hill then added Pilates to the mix, taking classes three times per week.

"It was so hard, but ultimately so worth it," she says. "My core is much stronger, and my arms are more toned. In fact, wearing a bikini on a magazine cover is my 41st birthday present to myself."