Don't Neglect Isometrics

More formally known as the Weider Iso-Tension Principle, this means flexing a bodypart, such as the abs, and holding that position (much like bodybuilders do when posing). To do this, tense each muscle for 6–10 seconds, then relax for 6–10 seconds. Repeat for 10–20 sets. This is a great way to hit your abs while sitting in your car, on your couch or at your desk.