The general principle is simple: whenever the body has been in one position for a while, it is good to briefly stretch it in an opposite position.

In a paper published recently, Kapur applied the principle of productive failure to mathematical problem solving in three schools.

The key principle of copyright law has always been that works can be copied only once?authors have expressly given their permission," says Piers Blofeld, of the Sheil Land literary agency?in London.

In contrast to each of these ideas, Covey advocates that leaders need to understand universal principles of effectiveness, and he highlights how vital it is for leaders to first personally manage themselves if they are to enjoy any hope of outstanding success in their work environments.