Credit: Shape Magazine

Britney Spears turned heads when she appeared on the June cover of Shape magazine in a white bikini, showing off a fierce new physique. So how did the 31-year-old mother of two get that hot new body?

Meet her secret weapon: trainer Tony Martinez. Martinez's star-studded client list includes Spears, Pink, Janet Jackson and many others. He now reveals the tricks to toning those famous muscles.

"I do compound movements …. two exercises at the same time," he told ABC News.

ABC News' Abbie Boudreau got a private workout with Martinez and tried out the hardcore routine he does with Spears. It includes a mix of exercises from such sports as basketball and football, and treadmill exercises and ab workouts.

"I just want to make it fun," Martinez said, adding that he pokes fun at his A-List clients to keep them motivated.

"Like … 'A little kid could be doing this,' you know'?" he said with a laugh. "So, that's the point. It works out great."

To get a body like Spears', Martinez says you need to follow the "four B's": basketball jump shot against the wall 20 times; backward interval walking on a treadmill at 2 mph for 1 minute, then walk forward for 1 min; balance on one leg, then with one arm doing medicine ball slams; bicycle and rotate on the floor mat 20 times to get Spears' abs.

Watch the piece to see how Boudreau fared and check out a Martinez's breakdown of the routine.

Every exercise is 20 seconds long with a 10-second rest in between. Martinez suggests doing three to four sets of each exercise. Some of the exercises use CoreDiscs, which are a part of Tony's TravelFit product line.

1. CoreDisc side lunge while dribbling basketball, then jump shot

The lunge works the inner thighs and core, and the jump shot simultaneously works legs. This is one of Spears' favorite movements.

2. CoreDisc lateral slide with football toss This works the core, legs, chest and shoulders.

3. Softball swing squat

This works the legs and core.

4. Band push-pull (lateral row)

This works the back and is cardio.

5. Flamingo

This works on chest, core and balance.

6. CoreDisc circles left/right and alternate front raise

This one works on core, shoulders and triceps.

What does Britney eat to stay fit? Click here to see her grocery list that went viral.