Set your feet shoulder-width apart and rest your hands loosely behind your head, elbows out. Lift one knee to the other elbow while tightening obliques. Flip the other side and alternate sides carefully.
Place your feet hip-width apart. Lift one knee to your chest while contracting your abs. Lower the knee and repeat with the other.
Stand tall with feet together. Lift one leg out to the side with a straight leg and core engagement. Reverse the leg without touching the ground and repeat on the other side.
Stand with hands loosely behind your head and feet shoulder-width apart. Bring one knee to your chest and rotate your body to bring the other elbow to it. Switch sides while pedaling.
Place your feet hip-width apart. Raise one arm above and reach for the other foot. Reach down and engage your core to return to the start. Swap sides.
Stand with knees slightly bent and feet hip-width apart. Lean back slightly with your core engaged and back straight. Hold your hands together in front of you and rotate your body right and left, working your obliques.