Sit on the deck and bends both knees while feet are kept together and held slightly above the ground
Torso is kept straight with the back kept off the ground at a 45 degree angle with arms held together away from the body in a straight fashion and hands kept locked together like a ball or one can hold a weight to increase the difficulty.
Swing arms from one side to another in a twisting motion, with each swing to a side counting as one repetition. The slower one moves the arms from side to side, the harder the exercise becomes, working the abdomen that much better.
Do not stop between repetitions or else one will lose the effect of working the abdomen. Pay special attention to your breathing through the movement and make a point of not holding your breath. to ensure proper oxygen flow.
Perform each exercise for 30 seconds (back to back), then rest for 90 seconds. Repeat the circuit 4 times. Good luck!