The “only real” reason for a well-trained abdomen is to support overall body stability, which makes it necessary for a straight posture. A flat belly is not the right motivation, as I have explained before. Since every muscle has its antagonist, it is essential to work out the lower back as well. The muscles around the waist are often referred to as the “core” or “core muscles”. The following exercises are all done on the floor. Therefore, you should put a mat or a towel underneath to make the exercises more comfortable, and the mat will keep you from getting cold. If you are not certain if your body is completely straight while exercising, ask somebody to check and correct your posture until you are doing it right yourself. Even I need to be corrected sometimes. A mirror next to you can also be an excellent aid. Small muscles can do more repetitions with fewer breaks in between each set. I would suggest that you do one set of each of the exercise below and then start over with the first one. Go through all at least three times.