In recent years, training volume has been well-studied in the resistance training literature. A recent meta-analysis by Schoenfeld and colleagues showed a dose-response relationship between training volume (in terms of weekly sets) and muscle hypertrophy. However, some research has suggested an upper-limit to this relationship, whereby additional weekly sets do not translate to more muscle growth.
This study investigated the effects of three different training volumes on lower-body hypertrophy in well-trained lifters. 35 males participated in this study. Subjects had at least 3 years of training experience, and could squat at least 1.5 times their body mass. Using a balanced and parallel group-design (based on previous training volume performed), subjects were randomly assigned to perform 12, 18, or 24 sets per week for the quads.
All groups performed 2 training sessions per week for 8 weeks, and quad training was equally divided between the back squat and leg press. Training sets were performed to 2 reps in reserve for each exercise, except for the last set which was taken to concentric failure.
The researchers found that all three groups experienced significant increases in quadricep muscle thickness, with no significant differences between groups. Additionally, the researchers performed a sub-analysis dividing each subject into separate tertiles, based on changes in muscle thickness.
On average, the low responders increased training volume from previous training by 1.8 ± 6.7 sets per week, the moderate responders increased training volume by 4.3 ± 9.3 sets per week, and the highest responders increased training volume by 6.6 ± 12.4 sets per week. This shows that while some subjects who saw the most hypertrophy increased their training volume substantially, others actually decreased their training volume.
A recent study by Scarpelli and colleagues found that when subjects increased their training volume by 20% above baseline, they saw significantly greater growth than a fixed volume increase, providing additional credence to the utility of individualizing volume progression.