The 'tone zone' for lifting, with approximately 13 reps per set, is considered a holy grail for muscle growth.
"if you're going for strengthen size update reps per set if you're going for mostly size eight to twelve reps per set and for endurance go for 14 or more reps per set now you might be wondering what about 13 reps per set and this is really the holy grail of lifting and what we call the tone zone"