There are positions that support the use of large muscle groups and positions that don't. The aim of the game is to be in a position to leverage the greatest portion of your strength while, ideally, placing him in a position where he can't do the same.
Or so the answer to that would go.
yeah but the only problem is that the moment your opponent (or partner) feels your strength he/she will resist. If you are relaxed and utilise Ki it will be harder for them to stop you. This can be evidenced through static gripping such as katatetori where the moment you use strength anyone strong enough can stop you by resisting.This tends to happen when you mind and body are together, which is not how me and the other students are trained