If you're starting to train the abs, it's very important to be careful as well as to know how to do it correctly. Some examples of exercises are:
- The plank: in which you have to maintain without touching the floor during some seconds little by little.
- The crunches: in which you lie ok your back with your knees bent and feet flat on the floor
- The russian twists: in which you sit on the floor with your knees bent and feet lifted off the ground
- Leg raises: in which you lie on your back with your legs straight.
also, you can try the exercises of the picture. Wish you the best!!