What do boys mean by abdominal muscles 99-90?

Boys say that abdominal muscles are 99-90, which means that 9 abdominal muscles have become a piece of fat.

1, abdominal muscles are the muscles of the abdomen.

2, 99 is one, that is, 9 abdominal muscles have become a whole piece of fat because they have not exercised for a long time and overeating. Therefore, boys say that abdominal muscles are 99-90, which means that all nine abdominal muscles have become a piece of fat. Abdominal muscle is an important part of human connective tissue, which refers to the muscle group of human abdomen, mainly including rectus abdominis, oblique abdominis, oblique abdominis and transverse abdominis, which can stabilize lumbar spine.