Well, I haven't started medical school yet, so I can't comment on that (though I am not only pre-studying if you consider testing the effect of ethanol on human physiology and behavior to be pre-studying), but in my experience, pre-studying for undergrad courses is fairly useless. In my classes, required knowledge was defined by what the professor tailored their classes towards, so until you had the syllabus, lecture materials, etc, you wouldn't be able to focus on what was important for that class, so doing something like reading the textbook may give you a general overview of the field the course was on, but would not give you targeted information about the specific topics covered in that particular class. Thus, trying to pre-study "blind" would only result in inefficient use of time and energy. Be aware, however, that this is only specific to my own experiences and may differ in cases where professors tend to teach the textbook, in which case pre-studying the textbook may have slightly more value (though I still wouldn't recommend it for a variety of reasons).
