Understanding Muscle Growth: Reps vs. Weight Training

Question
I was wondering if you know who in your profession specializes in the knowledge of muscles? I have a question, but do not know how to write to.

My question is a confusion. I see people lift weights; some very heavy, but their bodies look like most other people. The I see others also lift heavy, but they do a lot of reps when lifting. Their bodies are massive. I am confused as to why doing lots of reps gives you big muscles vs lifting heavy with almost no reps. Same strength, but normal muscles. I thought that the heavier you lift, your muscles would naturally get bigger. Confused.

Answer
there is a lot more to developing big muscles than hi reps or hi weights.... a huge genetic factor.... some people can lift weights and there muscles won't get big and others develop big muscles.  Some people cheat and use anabolic steroids.  You are right in general though, if you talk to a trainer, the large muscled people are pushing the amount lifted up and up to increase muscle mass.