National Council on Strength & Fitness
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How to Develop Muscle Mass

When attempting to increase one’s lean muscle mass, it is important to realize that several factors play key roles in this process and that the interaction among these components can greatly affect one’s success in this endeavor. Focusing too intently on a simple aspect such as resistance training, or neglecting a given component, such as nutrition can have a direct influence on muscle development and the degree to which it occurs. One key factor involved with increased muscular growth is related to body composition. Body composition, or the relationship between fat mass and fat-free (lean) mass, is an individual factor that is based largely upon genetic predispositions and voluntary activity participation. In fact, it is estimated that approximately 20-40% of an individual’s current muscle mass and their ability to alter the amount of muscle mass they maintain can be attributed directly to genetic. Therefore, 60-80% of an individual’s muscular make-up is alterable with proper diet and exercise. An individual who genetically is predisposed to have a larger proportion of fast-twitch muscle fibers (Type II) than someone else would have the ability to increase their hypertrophic response to training due to Type II muscle fibers’ propensity to increase diameter with progressive overload. These muscles tend to respond very quickly to anabolic hormones heightened during training and, with proper nutrition, these muscles will grow more quickly than slow-twitch muscle fibers. In contrast, having a greater number of slow-twitch muscle fibers negatively effects hypertrophy training, but can increase one’s ability to utilize oxygen during aerobic metabolism and thereby prolong exercise time until exhaustion. This corresponds with an increased ability to perform endurance type activities.


As mentioned above, genetic predisposition accounts for some degree of variability with regard to an individual’s muscle mass and their ability to increase that mass. Two components that can be controlled on an individual basis are nutrition and exercise participation. The nutritional component is related directly to the amount of energy-yielding nutrients consumed on a day-to-day basis. The USDA recommends that a healthy, well-balanced diet consist of approximately 55-60% carbohydrates, 10-15% protein, and less than 30% from fats. When examining the makeup of muscle, it is clear that these nutrients play a role in muscular development. The consistency of muscle is approximately 70% water, 22% protein, and 8% carbohydrate and minerals. A safe recommendation for an individual looking to increase their lean mass is an increase of approximately 150-200 calories above the daily need. It is also recommended that the majority of these calories come from protein. Important to note is the fact that additional caloric intake above this range can be associated with increased fat storage. Individual daily increases above 500 calories, even if from primarily protein, will not necessarily result in additional muscle mass. Due to the fact that protein synthesis is closely regulated, adding more protein has the least impact on outcome, when compared with training and the associated hormonal response. In fact excess protein intake without adequate carbohydrates can lead to a dysfunctional protein sparing mechanism. Blood lipid profiles can also be negatively affected by increased caloric intake if fat consumption is above the recommended daily allowance. Whenever the number of calories being consumed exceeds the number of calories expended weight gain will occur. The ideal situation would couple resistance training; specifically hypertrophy training (which will be discussed in detail below) with a moderate increase in calories predominately from protein.


In addition to the required caloric increase, specific training programs geared toward maximizing increases in muscle mass are necessary. A number of factors must be considered when training for hypertrophy. Perhaps one of the most important, and more often overlooked principles, is the muscle experience. Research shows that the greatest increases related to hypertrophy training occurred in individuals who had been training for at least 2 years in a structured resistance program. This most likely relates to the development and increased efficiency of the anaerobic metabolic pathways and hormone receptors. The high volume, moderate-high intensity coupled with short rest periods creates a hormonal environment ideal for muscle growth. The physiological disruption and blood pH causes an increased release of testosterone and cortisol which act to increase growth hormone, consequently causing the liver to release Insulin-like Growth Factor. Individuals completing resistance training programs must make sure that their increase in training volume coincides with their increased caloric intake so that the anabolic hormones released in response to resistance training will have the caloric support to increase muscle development.


Even with increased caloric intake and intense resistance training everyone will still reach a point where their muscle development will plateau. This is a result of an individual’s body becoming less prone to release the anabolic hormones in response to the training. At this point, there may be an unrelenting sense of frustration that sets in upon the individual when results are not as prevalent. However, a program known as periodization training is essentially a training technique that cycles through different programs (hypertrophy, strength, endurance, etc.) that consistently place a new stress on the muscle. By progressively overloading the muscle and ensuring that adaptation responses continue to occur by altering training regimens, an individual is able to maximize muscular development and the increase in lean mass.


Periodization training is a technique where you vary the intensity of training cycles (or periods) which will, among other things, alter the levels of the anabolic hormones released by the body. By changing concentrations of anabolic substances released by the body in response to training, it in effect, will help an individual maintain their sensitivity to these hormones to better facilitate muscle development. Very specific set, rep, and rest interval schemes are established for each training regimen. They are outlined in the chart below. Typical periods last between 5-8 weeks. The important concept to keep in mind with hypertrophy training is the rest intervals. The majority of individuals who participate in resistance training on a regular basis will only partially complete a hypertrophy cycle. They complete between 8-12 repetitions of an exercise at 70%-85% of their 1-RM. The reason most individuals don’t see the increased muscle mass they strive for is a result of incorrect rest periods. Muscular hypertrophy is maximized when rest intervals are between 30 – 90 seconds. Longer rest periods reduce growth hormone release.


From a personal training standpoint, understanding periodization training will be a key concept that can greatly effect the goal attainment of your client base. Incorrect programming will prevent clients from achieving their goals. While a large majority of a trainer’s clients’ primary goal will be weight loss, a handful of clients will be looking to add lean mass. When factors such as nutrition and proper resistance training programming are used cooperatively, an individual can safely and effectively add muscle mass while not compromising body fat percentage or blood lipid profiles.

Muscular Hypertrophy
Sets Reps Rest Interval Percentage of 1 RM
3-6 8-15 :30-1:30 min 70%-85%
Muscular Endurance
Sets Reps Rest Interval Percentage of 1 RM
2-3 15-20 :30-1:00 min 50%-70%
Muscular Strength
Sets Reps Rest Interval Percentage of 1 RM
3-6 3-6 2:00-3:00 min 75%-95%
Muscular Power
Sets Reps Rest Interval Percentage of 1 RM
4-8 2-5 > 3:00 min 80%-95%