Buttocks and hamstrings
Lie on a mat on your back with hands crossed on top of chest. Place one foot flat on the mat, with knee bent, and raise other leg, resting heel of foot on stationary leg, as shown. Lift hips about six inches off ground, and hold for three seconds. Lower to start. Perform all reps, then switch legs to equal one set.
Challenge yourself: Extend raised leg toward ceiling for an added core challenge.