Planks for 10 seconds ?

Take this new "McGill'ism" with a grain of salt and in the context it may have been given, ie. for general core strength for the average person.
For what we do however, we do not agree this is a rule to follow. In our clients, when working on functional stability deficits, adhering to a 10 second rule won't often make sense to resolve the issues of planar skill, endurance or strength deficits.