Windmill

A good exercise for developing your abdominal and adductor (inner thigh) muscles, however should be avoided by beginners.

Lie on your back, with your arms extended out to your sides to aid your balance, avoid using your arms to help you lifting your legs up.

Place a suitable sized Swiss Ball between your heels, with your legs straight.

Keeping your legs straight aim to rotate the ball around in a smooth horizontal circle, by bringing the ball up to your chest, then around to one side, away from your body then finally back up to the other side.

Focus on keeping the movement smooth and slow, beginning with small movements to help warm-up the muscles being used, gradually increasing the size of the circles.

You may want to work in 1 direction at a time, or alternate with each complete circle.

Avoid lowering down to far, as this will cause an arch in your back, which increases the stress on your lower back muscles and joints.

All levels should aim to work for a comfortable amount of reps maintaining good form throughout.