good posture

Old injuries are often hindered from fully healing due to the way we hold tension, and the protection mechanisms we put in place (i.e. tension) for an acute injury often turn into secondary issues later on when we habituate that tension pattern beyond it's initial useful period.
After millions of years of evolution you can rest assured that your postural reflexes work well enough if you don't interfere with them. You could say good posture is simply a lack of bad posture. Although good and bad are such judgemental words. You either have poise or you don't.
There are several causes of period pain, and one of the biggest ones I see is a structural issue also known as a wondering womb. This is where the uterus is no longer in her optimal position, she can be too far forwards, backwards, to one side or another and even flexed over in either of these positions.
Good posture isn't something you do, it's the by-product of not pulling yourself out of natural balance/alignment. It is bad posture that is caused by doing. Evolution has left us with postural reflexes that work just fine if we don't interfere with them. But why do you pull ourselves away from poise and ease?
Cynical click-bait headline aside, I'll cut to the chase, they don't work. There, I said it. But let's look at why that is, there are three main reasons...
Pilates combines resistance training with flexibility, which helps you build leaner, less bulky muscles. Combine long muscles with better posture and you'll naturally start to feel lengthened. The end result: when you feel taller, you look taller!