Hanging ab crunches- good/bad...

Can someone please provide information on hanging ab crunches, concerning proper form, usefullness, and potential injuries (not including falling off the bar).

Which way you hangin'? By your hands or by your feet?

Feet. Well, knees actually. I tried to find those hang-boots, but couldn't, so I just grip the bar with my legs bent at the knees and crunch away.

Vedran.

There isn't anything you can only accomplish by upside-down crunches. I remember Richard Gere doing them in that movie in which he played a gigolo (sp?) but he had boots that hooked over his bar.

You can do the more traditional 'hanging' leg raise by hanging by your hands from the chinup bar and raising your straight legs - that's a good ab exercise and will work your grip as well.

My preferred ab exercises are 4: 1) deadlifting, 2) a $10 plastic wheel on a stick on which I do rollouts from a standing position, and 3) a move called the Full Contact Twist where you stick one end of a barbell into a corner, load a few plates on the other end, and stand up, holding the bar about head high in front of you with locked elbows. You then let the bar come down to one side as you turn your feet 90 degrees, bending your elbows and knees a bit - that's the negative portion - then you lock your elbows and twist back to the starting position, leading with your hips. It's a cool exercise for the side muscles in your midsection. 4) suitcase deadlifts with a barbell or one-armed farmers walks with a kettlebell.