swiss ball oblique crunch

Obliques, rectus abdominus, transverse abdominus

Swiss ball, bench

Lie on the Swiss ball in the position shown below.

Hold onto a stationary object for balance, and bring your opposite elbow to knee.

Return to the start position, completing a whole set on one side before turning around and repeating on the other.

OPTION - let go of the object you are holding onto. This will challenge your balance as well as core strength.