The Overload Principle: A Key Concept in Strength Training for Muscle Growth


Strength training for muscle growth is a complex process that requires careful consideration of various training variables to maximize gains. One of the key principles in strength training is the overload principle, which states that exercise must be sufficiently challenging to cause changes in the body and tissues. The overload principle encompasses acute and progressive overload, essential in strength training for muscle growth. (Zatsiorsky & Kraemer 2006)

Acute overload refers to the fact that the stimulus of a single exercise must exceed the threshold that triggers physiological changes. For example, in strength training for muscle growth, acute overload is generally achieved by varying the strength training variables, such as volume, load, and distance to failure, to suit the trainee's level and individual characteristics (Israetel et al., 2021).

On the other hand, progressive overload refers to the fact that the exercise must become progressively more challenging to induce changes in the body. Progressive overload is essential in muscle-growth strength training, as maximal strength develops through four adaptations: an increase in muscle cell size, an increased ability of muscle cells to generate force in proportion to their size, an increase in the number of active muscle cells, and increased tendon stiffness (Kraemer & Ratamess 2004)

In practice, progressive overloading involves considering the adaptations caused by previous exercises in future exercises. For example, after an exercise with heavy loads (1-5 RM), several adaptations that develop maximal strength are stimulated, while moderate or light loads (6-30 RM) mainly stimulate muscle cell growth. Therefore, progressive overload can be implemented in the next exercise by slightly increasing the load or performing more repetitions with the same load 

In a strength training exercise aimed at muscle growth, a sufficient number of stimulating repetitions stimulate muscle growth. Stimulatory repetitions for hypertrophy cause the muscle cells of high stimulus threshold motor units to shorten slowly and produce a lot of force, thus experiencing a high mechanical load. This occurs when lifting heavy loads (1-5 RM) and when lifting medium or light loads (6-30 RM) close enough to failure (Beardsley, 2019).

As muscle cells increase in size, they can produce the same amount of force while recruiting fewer motor units, improving the muscle's ability to produce force. Therefore, doing exactly the same exercise (sets x reps x load) as the previous session will no longer include the same number of repetitions that stimulate muscle growth. Instead, the load must be increased to achieve the same number of stimulating repetitions, or more repetitions must be performed with the same load (Schoenfeld 20210).

In conclusion, the overload principle is crucial in strength training for muscle growth. Acute and progressive overload are essential in inducing changes in the body and tissues, and it is vital to vary strength training variables to suit individual characteristics. Progressive overload allows for progressive training, ensuring that the exercise continues stimulating muscle growth by becoming progressively more challenging. By understanding the overload principle, individuals can tailor their strength training programs to achieve optimal muscle growth and overall fitness.


Beardsley, C. (2019). Hypertrophy: Muscle fiber growth. Published by Chris Beardsley.

Israetel, M., Hoffmann, J., & Smith, C. (2021). Scientific Principles of Strength Training. Juggernaut Training Systems.

Kraemer, W. & Ratamess, N. A. 2004. Fundamentals of resistance training: progression and exercise prescription. Medicine and science in sports and exercise, 36(4), 674-688.

Schoenfeld, B. 2010. The mechanisms of muscle hypertrophy and their application to resistance training. The Journal of Strength & Conditioning Research, 24(10), 2857-2872.

Zatsiorsky, V & Kraemer, W. 2006. Science and Practice of Strength Training. Human Kinetics.