Its a common misconception that working one or two body parts a day is the proper way to divide your workouts. This is a fairly recent trend that has been circulating for the last number of years and was made popular by weight lifting magazines and internet columns. Two things happen when you attempt to divide your workout up in this manner. First you tend to overwork each muscle group (especially your smaller muscle groups) and second you only work each muscle group once a week in most cases. Remember INTENSITY is the key to great results not more exercises or more sets.