Reps: 10 per side
Lie face-up with arms extended, elbows slightly bent, into a wide 'V' overhead (open arms to the end of your towel's length), with towel pulled tight behind head.
Extend legs out at a 45-degree angle, bending right knee and pressing the inner edge of right foot against inside of left knee.
Lift head and shoulder blades off the floor. Keeping abdominals engaged, gently 'rock' to the right, balancing on right hip, using the right arm and your abs to help stop the movement. Return to center. Repeat 10 times to the right and then reverse 10 times to the left.