Research
In Ultimate Bodybuilding: The Master Blaster's Principles of Training and Nutrition Joe Weider says the following:
I learned that the best repetition range for building muscle mass is 5-8.
In the Wikipedia article on muscle hypertrophy, the recommended rep range is 8-12 reps:
Strength training typically produces a combination of the two different types of hypertrophy: contraction against 80 to 90% of the one-repetition maximum for 2–6 repetitions (reps) causes myofibrillated hypertrophy to dominate (as in powerlifters, Olympic lifters and strength athletes), whereas several repetitions (generally 8–12 for bodybuilding or 12 or more for muscular endurance) against a submaximal load facilitates mainly sarcoplasmic hypertrophy (professional bodybuilders and endurance athletes).
In contrast, the training program Shortcut to Size by Jim Stoppani on bodybuilding.com uses reps in the 12-15 range:
Barbell Bench Press - Medium Grip
4 sets of 12-15 reps
Rest-pause on final set
On stackexchange itself, this post links to a chart that recommends 6-12 reps for muscle growth. The confusion here is that the Wikipedia article above mentions 2-6 reps for strength improvements.
Feeling
It feels as though trainers, bodybuilders, and sport scientists cannot agree on the ideal rep range for muscle growth. This could be attributed to the mantra that "every body is different", but that's not very scientific.
Questions
- Is there an ideal rep range for increasing muscle mass, and if so, what is it?
- How much difference does the rep range make?
- Why is there so much contradiction between sources?
Update 1
I don't remember the name, but I read a book a couple of years back that contradicts the mantra that "every body is different" using the premise that human physiology is for the most part the same for all people, which feels plausible.
Update 2
One of the comments got me thinking about another mantra: "You gotta lift big to get big." It follows that by increasing the reps you decrease the weight, which eventually will mean you break that mantra. I suppose the truth of that mantra is for another question, but my feeling in this question is that Joe Stoppani's plan breaks it.
Update 3
An answer has caused me to question why rep ranges get so much focus. I started thinking about training intensity, which is often cited as needing to be high. I've started wondering if the reason rep ranges get so much focus is because it's easy to understand and measure when compared to intensity.