In the approach of Rav Natan, the disciple of Rav Nahman there is an emphasis to stay away from all secular learning, I think you can see in the LeM of Rav Nahman itself a somewhat different approach. This you can see in the first Torah lesson to להסתכל בהשכל שיש בכל דבר ולהתקשר להשם  על ידי השכל שיש בכל דבר to look at the wisdom that is in all things and to become attached to God by means of the wisdom that is in all things. But a vast majority of secular learning is pseudo science and so you can see why Rav Natan was taking the approach to avoid all secular learning all together. 

But since the Ran [Rav Nahman] himself had the approach of seeing the wisdom that is in each thing, it seem to me that this corresponds to the rishonim [medieval authorities] that held one ought to learn Physics [which meant at that time the book Physics of Aristotle and the related subject matter]. 

The approach of the rishonim however was not simply that book of Aristotle, but rather the subject matter. Even during the middle ages the subject was developing.