How to do scales technically?

Hello,


I have watched the first video by Andrew, explaining how to do scales. I could not understand everything as I am not a native English speaker. Does the wrist have to stay steady? I think I bend it too much on the side. Does it have to stay in the same line as the forearm? If the scales require to move the thumb under the fourth finger, is it possible to do it without moving the wrist?

I think I will have to go to the gym!

Hi! There is always need to be flexible in the wrist. You cant play piano without bending it. BUT, the more steady and still you can do it, the better it is for the speed, but a little bending is usually needed