The inverted-U of weekly sets
Training volume for hypertrophy is usually counted as the number of hard working sets a muscle receives per week. The dose-response relationship is not a straight line: as weekly sets rise, growth tends to increase, then flatten as returns diminish, and eventually decline once volume outpaces the body's ability to recover and adapt.
This produces the characteristic inverted-U shape, where a moderate to high amount of well-recovered volume outperforms both very low and excessively high amounts.
Where the useful range sits
Reviews frequently point to a broad productive window of roughly ten or more hard sets per muscle per week for many trainees, with some individuals benefiting from more, but the exact peak is highly individual and depends on intensity, exercise selection, sleep, nutrition, and total training stress across all muscles.
Because the curve eventually turns downward, more volume is not automatically better, and chasing ever-higher set counts can impair recovery and progress. Volume is best raised gradually while monitoring performance and recovery. This is general educational information, not personalized programming advice.