No, they suck but do a lot of good,I am adding them in slowly but still do full body crunches. I like to rely on core getting hit doing other stuff haha.
I don't like them though...
.Having said that, I used to do these for a short period about 5 years ago:

"These" referring to the men or the exercise?
Pics are so small I cannot see actually.

Funny guy."These" referring to the men or the exercise?
Pics are so small I cannot see actually.

I haven't done them in a while, but I usually did one set to failure and timed it with the stopwatch on my phone. I remember starting off at about 1 minute 30 seconds, and eventually working myself to a personal record of about 3 minutes 45 seconds. I got tired of doing them because they are just so damn boring.Anyone else do planks? How long...seems to be differing opinion on where law of diminishing returns begins. In any event, it's good stuff.