Low to moderate volumes are sufficient to promote increases in strength. A 2017 meta-analysis reported that performing ≤ 5 sets per week substantially increased strength, with slightly greater gains with higher volumes.[1] There was insufficient data to determine whether 10-12 sets per week produced greater strength gains than 5–9 sets per week.
Other evidence indicates that performing 3–6 sets of 1–5 repetitions per week using loads ≥ 80% of 1-repetition maximum (1RM) and ending sets approximately 1–4 repetitions shy of muscular failure promotes meaningful increases in 1RM strength in resistance-trained individuals.[2]
Higher volumes don’t appear to provide benefits beyond that of low to moderate volumes, and might even be detrimental for strength gains by causing greater amounts of fatigue and delaying recovery from exercise. A study in resistance-trained men found that performing flat barbell bench press and barbell military press three times per week for a total of 6 sets per week was as effective as performing 18 or 30 sets per week for increasing bench press 1RM, and performing barbell back squat, leg press, and leg extension three times per week for a total of 9 sets per week was as effective as 27 and 45 sets per week for increasing squat 1RM.[3] Similarly, a 1997 study in resistance-trained men found that performing 4 sets of upper-body presses once per week was as effective as performing 8 or 16 sets per week for increasing bench press 1RM, and performing 3 sets of quadriceps exercises per week was as effective as performing 6 or 12 sets per week for increasing squat 1RM.[4]
A potential limitation of these studies is that the participants were instructed to perform each set to muscular failure. However, a meta-analysis currently in the preprint stage reported that lower-volume, lower-effort (i.e., sets were stopped further from muscular failure) resistance exercise programs produced similar (potentially greater) gains in lower-body strength than higher-volume, higher-effort programs.[5]