Well my sons both returned from their hols at the weekend and I told them (separately) about these exercises. They were doubtful that I could even do them,,,,,so I showed them and they were both well impressed. My younger son had been doing them on holiday because one of his mates does them too......I now have a few variations of the plank to try! It's funny because while that son was at uni discovering low carb eating, I was at home doing the same thing, so we compared notes when he came home for hols....now we've done the same with exercise.