Ninja Abs

In ninja abs, what you have to do is to put your hands closed and your elbows in the ground parallel to your body with your arms making a 90º angle, then with your body completely straight you have to put your feet on the floor, and once you are in that position all you have to do is to raise one of your arms and stretch it forward punching the air, then you have to get back into the position and do the same movement but with the other arm, and then going back to position again. Keep alternating your arms and hold as much repetitions you can.

Details: Always keep your body straight and the 90º angle with your arms. Try to find something fluffy to put under your elbows.