In resistance training the volume of exercise is the summation of the total number of repetitions and sets of a particular exercise during a single exercise session multiplied by the resistance used. The same combination of repetitions and sets is not and should not be used for all muscle groups.

There is an inverse relationship between the number of repetitions performed and the intensity of the resistance. The higher the intensity (load), the lower the number of repetitions that are possible; and conversely, the lower the load, the greater the number of repetitions possible. Therefore, the exercise load directly dictates how many repetitions and sets are possible.

Repetitions. The number of repetitions in a dynamic exercise program refers to the number of times a particular movement is repeated. More specifically, it is the number of muscle contractions performed to move the limb through a series of continuous and complete excursions against a specific exercise load.

If the RM designation is used, the number of repetitions at a specific exercise load is reflected in the designation. For example, 10 repetitions at a particular exercise load is a 10 RM. If a 1 RM has been established as a baseline level of strength, a percentage of the 1 RM used as the exercise load influences the number of repetitions a patient is able to perform. The “average,” untrained adult, when exercising with a load that is equivalent to 75% of the 1 RM, is able to complete approximately 10 repetitions before needing to rest. At 60% intensity about 15 repetitions are possible, and at 90% intensity only 4 or 5 repetitions are usually possible.

For practical reasons, after a beginning exercise load is selected, the target number of repetitions performed for each exercise before a brief rest is often within a range rather than an exact number of repetitions. For example, a patient might be able to complete between 8 and 10 repetitions against a specified load before resting. This is sometimes referred to as a RM zone; it gives the patient a goal but builds in some flexibility.

The number of repetitions selected depends on the patient’s status and whether the goal of the exercise is to improve muscle strength or endurance. No optimal number for strength training or endurance training has been identified. Training effects (greater strength) have been reported employing 2 to 3 RM to 15 RM.

Sets. A predetermined number of repetitions grouped together is known as a set or bout. After each set of a specified number of repetitions, there is a brief interval of rest. For example, during a single exercise session to strengthen a particular muscle group, a patient might be directed to lift a load 8 to 10 times, rest, and then lift the load 8 to 10 more times. That would be two sets of an 8 to 10 RM

As with repetitions, there is no optimal number of sets per exercise session. As few as one set and as many as six sets have yielded positive training effects. Single-set exercises at low intensities are most common in the very early phases of a resistance exercise program or in a maintenance program. Multiple-set exercises are used to progress the program and have been shown to be superior to single-set regimens in advanced training.

Training to Improve Strength or Endurance: Impact of Exercise Load and Repetitions

Overall, because many variations of intensity and volume cause positive training-induced adaptations in muscle performance, there is a substantial amount of latitude for selecting an exercise load/repetition and set scheme for each exercise. The question is: Is the goal to improve strength, muscular endurance, or both?

To Improve Muscle Strength

In DeLorme’s early studies three sets of a 10 RM performed for 10 repetitions over the training period led to gains in strength. Current recommendations are to use an exercise load that causes fatigue after 6 to 12 repetitions for two to three sets (6 to 12 RM). When fatigue no longer occurs after the target number of repetitions has been completed, the level of resistance is increased to once again overload the muscle.

To Improve Muscle Endurance

Training to improve local endurance involves performing many repetitions of an exercise against a submaximal load. For example, as many as three to five sets of 40 to 50 or more repetitions against a low amount of weight or a light grade of elastic resistance might be used. When increasing the number of repetitions or sets becomes inefficient, the load can be increased slightly.

Endurance training can also be accomplished by maintaining an isometric muscle contraction for incrementally longer periods of time. Because endurance training is performed against very low levels of resistance, it can and should be initiated very early in a rehabilitation program without risk of injury to healing tissues. Remember, when injured muscles are immobilized, type I (slow twitch) fibers atrophy at a faster rate than type II (fast twitch) fibers. This underscores the need for early initiation of endurance training.

Exercise Order

The sequence in which exercises are performed during an exercise session has an impact on muscle fatigue and the adaptive training effects. When multiple muscle groups are exercised in a single session, as is often the case in rehabilitation or conditioning programs, large muscle groups should be exercised before small muscle groups and multijoint muscles before single-joint muscles.In addition, after an appropriate warm-up, higher intensity exercises should be performed before lower intensity exercises.

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