I am not Catholic and rely only on the history I have read.
Wasn’t this common practice for both preists and nuns in the not too distant past?
Pope John Paul was not a young man. Perhaps he carried on with the practice?
Some still practice self-flagellation; sleeping on the concrete floor; etc.
I believe the Cursillo teaches these practices.
I always found them to be self-defeating.
Life is hard enough without beating yourself up.