This circuit based workout will engage your entire core and really fatigue your abs and obliques. Spend no longer than 30 seconds on each exercise and then change. Once the circuit has been completed once, take 30 seconds rest and then repeat 4 more times (5 sets).

Hanging leg raises – 30 seconds

Cable pull down crunch – 30 seconds

Sit ups – 30 seconds

Double crunch – 30 seconds

Oblique teapots – 30 seconds