I don't get it...why would you use these things to prepare for the LSAT? You're much better off spending that time doing practice tests or working on the LG Bible or something. When I took the LSAT, I do not recall ever thinking "darn, I wish I'd read Plato's Republic or this month's Scientific American!"
It's kind of like stretching before lifting weights. It helps to condition your brain when 1) you don't want to be actively studying 24/7; and 2) you want to pace yourself so you don't run out of prep material (like me). I've only had two years of high school science and that was like 10+ years ago, so when I see phrases like "iridium-rich earth mantle layer" or "gamma-aminobutyric acid", I freak out. Exposing myself to magazines like Scientific American or even Popular Science gets me used to scientific mumbo jumbo and helps to alleviate my anxiety.