When you lift weights, your workout will usually specify a specific amount of sets that each exercise should be practiced. A set describes a group of repetitions that a specific exercise is performed. For example, performing squats for three sets of ten reps means that you will choose a weight heavy enough that you can only complete 10 squats in a row, followed by a short break then repeated two more times for a total of three sets.
In order to determine the most optimal amount of sets that should be conducted for an exercise we look at the current research. A study was conducted on forty-eight men with no weight training experience, with the purpose of comparing the response of 1, 3, and 5 sets against improvements in strength and muscle growth. Each participant performed 3 resistance training sessions per week for six months. The results of this study showed that the 5 repetition maximum for bench press, lat pull down, shoulder press, and leg press increased the most within the 5 set group, followed by the 3 set group, with the smallest increase in the 1 set group. Additionally the 5 set group had the largest increase in muscle thickness, followed by the 3 set group, with the smallest increase in the 1 set group. The study also concluded that all the groups decreased their percent body fat, increased fat free mass, and vertical jump ability with no difference between the groups.
The results from this study suggest that if your primary goal is to increase muscle mass you should perform 5 sets of each exercise, if your goal is to become more toned and loose fat you will get the same results with lower set ranges.
Study can be accessed here: Dose-response of 1, 3, and 5 sets of resistance exercise on strength, local muscular endurance, and hypertrophy