Description of the reverse crunches (part 2):
Count to three. Then keeping your back straight and your chin lifted, curl your knees in toward your chest. Your lower legs now are parallel to the floor. Count to three again. Slowly return to the start position and repeat. Count at every position to three.
It is very important that you do this exercise very slowly. So count at every position to three. You can wait more than 3 seconds, if you want or need a delay, but you legs are always in the air.
Attention: Don’t let your legs or the bottle touch the floor before your have done all 10 reverse crunches. If you have lost the bottle, you will start again until you have finished all 10 crunches.