One of the most frequently asked questions is how many repetitions should be done for each exercise. This is a valid question since the number of repetitions (together with the number of sets) is the key to the type of development that will be produced.
However, it is important to understand that there are no magical numbers that will produce the changes you desire. Strength, flexibility, muscle mass, and muscular endurance development are very individualistic. For some individuals doing a certain number of repetitions will produce the greatest increase in strength, flexibility, endurance, etc. while for others there will be minor changes. Because of this, you must pay close attention to the changes you receive from doing exercises with different numbers of repetitions in regard to your capabilities. There are, however, some excellent guidelines to direct your training based on research and practical experiences.
Following are some guidelines for the number of repetitions that should be used when the athlete is well experienced in weight training and has been in training in his sport for several years.
1-4 repetitions are for pure strength. There are no increases in muscle mass.
5-9 repetitions for strength together with muscle mass.
10-15 repetitions for muscular strength, muscular endurance, and muscle mass.
16-30 repetitions are for muscular endurance. There may also be small increases in muscular strength and/or mass.
31-50 repetitions are used for the development of muscular endurance, no mass and some cardiovascular endurance.
50-100 repetitions for muscular endurance, cardiorespiratory endurance, a possible loss of fat and
mass and no strength increases.
Keep in mind that these are only guidelines and there is variation in the numbers depending upon the individual and his or her stage of training. For example, high-level athletes who require increases in strength usually train in the 5-9 RM range, but not year round. Training with the same number of repetitions and weight leads to the hitting of a plateau (or full adaptation) in regard to increases in strength or other physical qualities.