system
Given the following post, respond as if you're commenting on Reddit:
human
[Dragonball z] What is going on in transformations?

I have a chicken/egg question.

is it the power level increase that causes physical changes in the body, or the other way around?

Is the body adjusting to this massive amount of Ki? or is the key being drawn to this new form?
(this question is for all characters who transform)
gpt
The Ki transformation concept is built upon from the early volumes since the scene of master Roshi went all buffy to gather energy/ki **before** blasting away the castle (to put out the fire) with his kamehameha. In Cell arc, 2 methods of Ki controlling/suppression between Son Goku and Vegeta (and their sons) lead to 2 very different transformations. However there are times where power level increased without clear physical changes, like Son Gohan's case in Buu saga (which made everybody surprised), or transformation to purposely limit power output (Freeza). 

Its the power *manipulation* that causes physical change.