It’s called ‘plank’ and has been around for a few centuries and still manages to be the most effective way to get your core in shape. It may have its roots in yoga- but the plank position is not just for those of us with a spiritual leaning. It is also considered a great exercise for polo players who need to work on combined back, leg and core strength and have not yet managed to get a horse into the gym for lunchtime practice.
The longer you hold your plank between rests, ideally three holds of fifteen to thirty seconds each, with a ten second break in between, the greater the work on your core. You can eventually graduate to holding for even a couple of minutes. The longer you don’t move a muscle the more you’ve accomplished!