And also you're missing the ""poetic"" in there, to overcome hell, victorious of a training you inicially thought it was pointless and abusive. It is to learn that you are strong and nothing can stop you if you put your mind into it.
I mean, there are clearly better ways to train with that in mind, just like they said.
The poetic side you're seeing here is plain barbaric and not recommendable at all.
When you're writing a book (a manga in this case), you're introducing people to a new way of life they're not supposed to know about, so giving shitty advice like this is not a sign of good writing and good mentality at all.
We let it go because it's clearly more focused on the drama than the sport part and because it's fantasy, but it's still bad writing and not recommendable at all, unlike what you said.
If you practiced any sport at all, you'd know you have to respect your body's boundaries if you want smooth progression on the long term, practice presented in this chapter sucks and should not be a standart to reproduce at all, obviously.
But again, it's a romanticised story about women being strong, so I can let this go as 'going too far' to make us understand this image of women being worst than men in sports in general, which isn't entirely wrong.
It's kinda awkward and dumb to do it like this, but it gets the point across without doing too much damage to the story, since it's been like this from the beginning, this manga's scenarios were never really meant to be close to tangible realities.