That will depend on how marked you want to have your abdominal muscles to know whether or not it is strictly necessary to train them in a very direct and intense, then when you want your abdominals to be very noticeable you have to squeeze them and do exercises that involve eccentric contractions and concentric alternating between them, that allow you to feel that you are forcing them to "go out" a little more and that you are forcing yourself to mark those muscular divisions of the rectus abdominus and the obliques in a very pronounced way and if what you want is to see yourself with a flat abdomen without marking so much because you do not like it or simply because you do not want to work so hard then you have the option of simply focusing on exercises that involve only isometric contractions such as the frontal, lateral plates, etc. or also simply keep your abdominal muscles tight or tight when you train other muscles of your body, remember that your abdomen will be very marked or it will not depend on your fat% that is low, because if it is high Any way you work you will never notice them, and the last no less important fact is the Food that is the key to everything with cardio.