If you're undertaking your CPL exams, you're generally going to spend a couple months hunching over a desk. By the time you've passed your IFR, your back is going to have spent hundreds of hours bent over your books.
One helpful trick to avoid this is to place a lamp directly above your table, by one way or another, and turn off the room lights. If you see your shadow on the desk, you'll know that you are hunching to far forward.
This technique has both improved my posture and shaved a couple dollars from my power bill.