Rather than outline each abdominal muscle, we'll use disconnected lines and dashes to merely indicate those shapes. This gives us a more natural, realistic look. When doing this, think of where the light would cast a shadow, and then add small marks until you achieve the desired effect. Let's go ahead and use dashed lines to add shadow to the pit of the neck, bottom of the shoulders, and the armpits. We'll let these areas of shadow help to define the forms.