While doing crunches is it best to?

Question

just do regular crunches? or use a ball ,or one of those ab machines?

bend your knees or not?

Answer 1

Depends on your goal. If you are trying to tone your stomach so to speak then the best method is through dropping bodyfat and doing high rep work eg. sets of 50. However if you are trying to increase ab muscle mass because you are already at a low bodyfat then you will need to do weighted ab work and keeping the reps between 5 and 20.

Crunches are not the best ab exercise in my opinion however when I used to do them I would bend my knees and put a weight above my head.

Look around reliable websites for new harder exercises. Try work up to weighted bridges for time and dragon flags.