I have just started doing planking, after being inspired by a friend's post on Facebook. I started yesterday and did 20 seconds. At five different times. Today I increased it to 30 seconds. My plan is to add 10 seconds a day until I finish the challenge in 28 days. I am not really planning to get a rack of muscles on my tummy. Just getting my pot belly reduced would be good enough. I have even taken photos of my tummy from my bird's eye view. I plan to take a photo each day for the duration of the challenge.
Has anyone done planking for a sustained period of time? How effective is it?