Ever read Poliquin? I'm looking at page nine in his book on strength. There's a chart about the "relationships between maximum number of repetitions, intensity, and the training effect."
Too bad I don't own a scanner. I'm poor. But let me briefly explain the chart:
It has rep and maximum weight columns. Reps start at "1" and increase. The other column features decreasing percentages of a given maximum. In effect, the two are inversely-related.
Around reps 9-12, corresponding to 76 to 70% maximum respectively, the greatest hypertrophy occurs. (That means mass).
Unfortunately, Poliquin presents no discussion about how roids can influence the chart. Complete denial, a la Arnold. (His picture's on the back, and he looks like he regularly sticks needles in his ass.)