[Matlock]

^The muscles which you can't normally see often contribute to strength. You also have to consider the tendons, ligaments, and bones. (All which can be trained, much like muscle)

Weight has little to do with it. For every person that is stronger and heavier than you, there probably is a person who is stronger and lighter than you.

Has no one seriously read this book? It's my favorite book of all time. Find it, buy it, or download it. It's the most useful read for strength.