Which effect is better and which is safer, belly roll or sit-ups?

Abdominal sit-ups are effective and there is no danger.

1, belly rolling is one of the most common abdominal exercises, mainly to exercise rectus abdominis. If you want to practice abdominal muscles, for beginners who lack exercise and lack of waist and abdomen strength, you can do abdominal rolling exercises first.

2, sit-ups, a way to exercise. Lie on your back, put your legs together, raise your hand, contract your abdominal muscles, swing your arms forward, and quickly become a sitting position. Keep your upper body bent forward, touch your feet with your hands and bow your head. Then return to the sitting position.