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By Evie Ullman DPT, CSCS

weight trainingA set is a group of repetitions, aka reps, of a weight lifting or strength training exercise. When a set ends, the exerciser rests for a given period, then he or she begins another set of reps, and so on and so forth. Sets and repetitions of a strengthening exercise can be varied depending upon the training goal. It is important to understand that the number of reps that can be completed is inversely related to the load lifted. Obviously, lifting heavier weight leads to fewer reps performed because fatigue sets in much more quickly. When working on healthy body parts, in most cases, sets of a strengthening exercise should be performed to the point of volitional muscular failure. Most of us have been there—your muscles burn heavily and your limbs begin to shake.  With a heavy weight you may reach failure at just three or so reps, and with a lighter weight you may perform upwards of 20 reps until you reach the point of failure.

For years, exercise physiologists have been conducting studies on the effects of different numbers of sets and reps and it is generally accepted that high volume training leads to an increase in muscular size and strength. Performing multiple sets is key for gaining strength, but in some cases only one set should be performed, i.e. if the individual is untrained or new to the exercise. Three sets of ten reps is a popular exercise prescription. Researchers DeLorme and Watkins originally developed this method, and it does build strength, but since then, other prescriptions of sets and reps have been studied and are proven to be more effective for specific exercise goals.  The rest period between sets also has an effect on training goals. There are many different strength training goals: muscular endurance, muscular power for a single-effort event, for a multi-effort event, etc. For simplicity’s sake, I will outline two different training goals: muscular strength and muscular endurance. The following guidelines are from the National Strengthening and Conditioning Association:

Number of reps for Endurance: 12+; Strength: 6 or less

Number of sets for Endurance: 2-3; Strength: 2-6

Rest period between sets for Endurance: 30 seconds or less; Strength: 2-5 minutes

In general, if your goal is muscular endurance, you should perform multiple sets of a high number of reps with a light amount of resistance and keep a very short rest period. If your goal is to increase strength (and muscular size), you should perform multiple sets of a low number of reps and allow for longer rest periods in between.

Dr. Ullman is a Physical Therapist at Boston Sports Medicine