1. If the subject has been injured before, especially waist injury, it is not recommended to do sit-ups;

2. If the subject is not injured and just wants to exercise, he can make a plan according to his current physical fitness, not too radical and step by step;

3. As for the plan, it is suggested that the subject try his best to see how much he can do first, then do at least 3-5 groups every day according to this figure, and then test and update the plan every week or month.

Good wishes!