while for repeated actions in the past

[Fremr]

Hello,
i would like to ask, if I want to use while for actions that were common in the past, do i have to use -ing after it?
For example:
I used to watch my mother while she cooked/ was cooking.
I used to study while my sister studied/ was studying too.

 

[5jj]

This (from here) may help.

While the use of the marked durative can show a longer action 'framing' a shorter one this does not have to be the case:

……13a. Sally was writing a report while Barry was preparing lunch.
……13b. While Sally wrote a report, Barry prepared lunch.
……13c. Sally wrote a report while Barry was preparing lunch.
……13d. While Sally was writing a report, Barry prepared lunch.


The writing and preparing are distanced in time. As they occurred in the past we know that the situations denoted are limited in duration (the duration does not extend to the present); the durative aspect therefore emphasises the duration more than the limitation. In [13a] the speaker emphasises the fact that the situations of writing and preparing extended over a period; in [13b] there is no such emphasis, merely a reporting that these situations actualised at the same distanced time. In [13b] and [13c] the suggestion is that the situation referred to using the durative aspect filled a longer time-period than the one referred to in the non-durative aspect. In these two sentences we can talk of one action 'framing' another.

 

[emsr2d2]

Hello.
I would like to ask something. If I want to use "while" for actions that were common in the past, do I have to use -ing after it?
For example:
I used to watch my mother while she cooked/was cooking.
I used to study while my sister studied/was studying too.