Celebrity trainer Joel Harper prescribes this tummy-firming routine 3 times a week on nonconsecutive days.
Place left foot on the first or second step of a staircase. Bend elbows, raising hands to shoulder height. With core engaged, slowly lift right knee to hip height, or as high as you can. Lower right foot back down and gently tap the floor. Repeat for 20 reps, then switch legs. Over time, build up to 3 or 4 sets per leg.
Lie faceup with hands at your sides, palms facedown. Lift straight legs to a 60-degree angle, keeping feet together and toes pointed. Slowly begin to circle legs clockwise for 25 reps, making an O the size of a basketball. Rest for 30 seconds, then repeat move in a counterclockwise motion. Perform series again, this time with feet flexed.
Start in the upper part of a push-up with 2 washcloths underneath the balls of your feet on a smooth floor. Engage core; slide right foot, bringing right knee in toward chest. Return right foot to starting position and repeat movement with left foot. Continue alternating knees as you count backward from 100.