These are 3 good and simple exercises to make your abdomen really strong and to make your core fit: “Knees-ups”, “Crunches”, “Side-planks”: you want to do them in a row or you can perform them separately, one exercise a day: anyway, you should sum a grand-total of 10-12 sets of 10-12 reps with just 5 seconds of rest between sets…Eat properly and train your abs every day, mixing these 3 exercises in different ways.