Bruce Lee's abdominal muscle training--"Raising the Flag"
This is the most intense, difficult and most effective abdominal muscle training I have ever seen:
Lying on a bench Go up, grab the bench behind your head with both hands, and lift your torso and legs straight off the bench (note: only the head and shoulders are in contact with the bench). When it reaches 90°, it is a flag raising.
Then keep your torso straight and slowly descend, without touching your feet, to continue with the next rep.
Beginners can start practicing from the elementary movements in Figure 2
