There are plenty of things you shouldn’t do on a gym ball. If you attempt any sort of dumbbell move you’ll be forced to drop the weight to first-day-at-the-gym levels, for instance, and any sort of circus trickery is likely to end in tears. But used correctly, your inflatable friend is one of the best tools in the gym. Its inherent instability means you’ll recruit dozens of tiny muscles as well as your major ones and keep them under tension during every rep. The workout here is specifically designed to give your abs a good going-over at the same time as testing the rest of your body. For best results, do every rep under control. 

How to do the workout
Circuits 3
Rest between circuits 90sec

Reps for each move
Beginner – 8
Intermediate – 10
Advanced – 12