Most of the core machines advertised on late night TV are garbage. Seriously. All hype and marketing. Those models have never used those machines to look like that. So don't get sucked in.
Crunches will not give you the sexy slim core you desire. In fact it takes 22,000 crunches to burn a pound of fat from a midsection. Who has time for that? Not you and I.
So where do you start? Start with exercises that work your whole body combined with core exercises that work your midsection the way it's intended. Like this...........
Work for 10 seconds and rest for 5 seconds and do 5 rounds. Not only does this work your entire core but your heart rate with skyrocket. Enjoy.