Where Do Set/Rep Schemes Come From?

Training Bodybuilding
1

Where do set/rep schemes come from?

I know that (generally):
high sets X low reps and long rests = strength
low sets X high reps and short rests = hypertrophy
high sets X high reps and short rests = endurance.

However, if a program calls for you to do 3 x 6, is there any inherent benefit of doing 3 x 7? How would results differ if you do 3 x 5?

Also, are there any good books that cover this topic?

2

Here’s a good article:

http://www.t-nation.com/readTopic.do?id=459411