Only books. I have looked pretty closely at them, but never have had any formal training or any sort of class, but probably should if/when I ever want to get back to the figure. I even have a thick, painted cadaver book that is gross to some people, but it's quite helpful for learning the body.
For some reason, this thread caught my eye. I am a retired podiatric physician, and studied anatomy of the entire body, spending a year dissecting a cadaver. I still have many anatomy books. And, no, I am not very good at figure drawing!