The plank and the side plank are often touted as a great core exercises.
This usually means that people ‘feel’ it in their mid section, but actually if you look at the mechanics of it, planks do a lot more than the work the core.
Rather than list all the muscles planks stimulates to contract, I find it easier to re-define what core means. Dr Gary Gray said it best when he described the core as “anything that connects the toes to the nose”.