People have been lifting weights for hundreds of years, yet we still can’t agree on the optimal number of sets and reps for building strength. Strength expert James Krieger performed a meta-regression that pooled the results of 30 treatment groups and 14 studies. He concluded that multiple sets (2-3 sets) per exercise produced greater increases in strength than single sets. Curiously, there were no differences between 1 set and 4-6 sets per exercise. He concluded that 2 to 3 sets per exercise caused a 46 percent greater increase in strength than one set in both trained and untrained people.
Training studies are extremely difficult. Typically, researchers use relatively untrained subjects who are minimally motivated. Genetic studies show that people vary widely in their response to exercise (i.e., there are responders and nonresponders). This study showed that 2 to 3 sets per exercise worked best for most people. Factors such as age, athleticism, motivation, adaptability, drugs, and supplements could influence the effectiveness of a training program.
Source: Journal Strength Conditioning Research, 23: 1890-1901, 2009