Octaves-grasping

when playing light octaves with the grasping motion then the hand muscles works and the by-product is that the wrist moves up and down-why not let the wrist bigger muscles ,which moves it up and down, do the work when playing a lot of octaves in a row and leave the smaller muscles in the hand? -in the vidoes of the octaves the teacher was showing the student how to play p octaves and she wasnt talking about the grasping motion, but rather showing the student just the up and down motion with the fingers,not the grasping motion. thank you

Because the smaller muscles very quickly go to sleep and stop doing their job. All muscles are involved in all movements, it's a question of fine tuning the degree of involvement. Sorry, I don't know what you are talking about. AFF