Yesterday, I was having my brain picked by a guy working-out at Cardinal Fitness. He had several questions about losing fat and training. Pretty generic stuff. Of course, I gave him a nice, long-winded answer including my training philosophy. Then he asked me what my thoughts were about ab-training. What exercises? What machine to use? When to train them? I told him that I do not train the 'abs' by isolating them with specific exercises, but they are integrated with full-body free-weight training movements. I also, mentioned that I felt it is a waste of time to perform old-fashioned crunches and the sort. He looked at me like a six year-old finding out that there is no Santa Clause. After pausing for a few seconds, he had a disappointed look on his face and said 'ok' and walked away.
The perpetual myth that 'Ab' training is going to help shed body fat from the mid-section and is the secret to getting strong (or even help with low back pain) continues to be well propagated. There is now much research to show that we do not need to isolate the abs (or more specifically do an exercise to isolate the rectus abdominus, transverse abdominus, internal, and external obliuqes). The abdominals stabilize the pelvis, rib cage,and spine with any movment. In fact, the torso muscles, including the abdominal muscles, are more challenged in the upright position with weights supported by the arms in an uneven manner (sounds like kettlebell movements)!
So, what are the best ab exercises? Everything my clients do: kettlebell swings, snatches, cleans, squats, lunges, deadlifts, presses, pull-ups, rows, push-ups, bear crawls, and farmer's walk.