The ‘hypertrophy [size gaining] range’ of roughly six to 15 reps per set may produce slightly better results per unit of time invested than low rep and high rep work.  However, on the whole, the advantage you get from working in the hypertrophy range isn’t nearly as big as people seem to think; maybe a ~10-15% advantage per unit of effort invested at most. ”

Greg Nuckols

author, powerlifter, and coach