These help tone your core and your butt. Especially the lower (typically looser) part of each.
Step 1: Lie on the floor with your arms on your sides.
Step 2: Lift your feet, bending both knees to 90 degrees so your thighs are perpendicular to the floor and lower leg is parallel to the floor.
Step 3: Slowly and quietly tap your left toes to the floor, then your right. This completes on rep
Step 4: Repeat
Image from rollingout.com
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