October 24, 2025, 3:42 pm | Read time: 4 minutes
Whether it’s a bigger bicep, broader back, or stronger thighs, building muscle is desirable not just for aesthetic reasons. Many fitness enthusiasts aim to grow their muscles without fully understanding the different types of hypertrophy training available. Fitness professor Dr. Stephan Geisler explains how they work and what should be done to achieve your goals.
Muscle hypertrophy is the scientific term for the increase in muscle mass through effective training stimuli. If we use the barbell in the gym correctly and consume enough calories and protein over a long period, it can lead to an enlargement of the cross-sectional area of the trained muscle. This can happen in different ways.
The 3 Types of Muscle Growth
We know that the enlargement of the muscle cross-section can occur in two to three ways:
- myofibrillar hypertrophy,
- sarcoplasmic hypertrophy, and
- hyperplasia.
Myofibrillar Hypertrophy
The myofibrillar form is the most well-known type of muscle growth and is also the most common goal in strength training. Here, the muscle cross-section is enlarged by the formation of tiny contractile units called “myofibrils” within the muscle cell. This not only makes the muscle larger but also stronger, which is why this form can be relevant for athletes.
Sarcoplasmic Hypertrophy
The sarcoplasmic form also describes an enlargement of the muscle cross-section. However, the muscle does not necessarily become stronger. Muscle growth is primarily achieved through the accumulation of fluid in the muscle cell rather than functional contractile units. This form can likely be achieved by adjusting the training plan.
Hyperplasia
Unlike the other forms, hyperplasia describes the formation of entirely new muscle cells, i.e., muscle fibers, which thickens the muscle. However, this form has only been demonstrated in animal studies so far. Therefore, we will disregard this form of hypertrophy in the following.
Thick Muscles Offer Health Benefits
A thicker muscle not only looks good but also brings a range of benefits, from reducing the risk of type 2 diabetes to buffering age-related muscle and strength loss (known as sarcopenia), potential protection against high blood pressure, and a positive effect on bone health, to a general performance boost (such as increased strength and power) across all population groups.1,2,3
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How Do I Achieve Muscle Hypertrophy?
Ultimately, it depends on the goal. Currently, it is believed that sarcoplasmic hypertrophy occurs more in the realm of higher repetitions with lower loads. In other words, a light weight (such as up to 60 percent of the 1-RM*) must be moved very often.
Additionally, we know that muscle hypertrophy can generally be achieved within a broad intensity range (such as 30 to 90 percent of the 1-RM) as long as the training is conducted close enough to muscle failure.
*Background: One Repetition Maximum
1-RM (1 Repetition Maximum) = the maximum load with which a clean repetition can be performed
The training volume, meaning how many sets per muscle group per week should be completed, strongly depends on the individual training condition. For beginners, however, four sets per muscle per week can be effective. This number of sets should naturally be increased over the course of training experience and distributed over several training days of the week.
Studies suggest that a muscle should be trained at least twice a week.4 Along with training frequency, the training volume can certainly be increased to around 20 sets per muscle group over two to three training sessions a week (bodybuilders).
Which Exercises Are Suitable for Muscle Hypertrophy
This also depends on the goal. Muscles can be built with machines, cable pulls, free weights, and even with one’s own body weight. The important thing is to adhere to the described load norms (especially the number of repetitions and sets, intensity, and training frequency) and to transition from more complex, free multi-joint exercises (such as free weight squats) to less complex machine or single-joint exercises (such as leg extensions). This is because a fatigued muscle poses a greater risk of injury during more complex exercises.
Otherwise, small but significant differences in exercise variations and the involvement of individual muscles can actually be detected with various investigative tools. For example, it is known that the leg extension targets certain parts of the thigh muscle (rectus femoris) more than the squat does. So, the choice of exercise is not unimportant.