Building muscle is a complex process influenced by various factors, from exercise selection to nutrition and recovery. An ineffective program can not only lead to suboptimal results but can also cause muscle tissue loss. 

On Aug. 27, 2024, Gommaar D’Hulst, a Senior Scientist and Muscle Biologist at ETH Zurich, delved into the possibility of losing muscle despite regular strength training.

Muscle building is an energy-intensive procedure. A comparative study suggests that muscle protein synthesis is the second-most energy-demanding process within a cell. (1)

You need a surplus of approximately 6,700 calories to build one kilogram of muscle.

The body efficiently allocates energy, and muscles not specifically engaged during training could potentially atrophy over the long term.

A study published in the Medicine and Science in Sports and Exercise journal examined the impact of targeted resistance training on muscle growth. Twenty-one untrained individuals participated in a supervised, 10-week program focusing on single-joint exercises that engaged the entire body. (2)

MRI scans were used to measure the total volume of 17 recruited and 13 non-recruited muscles before and after the program, providing insights into the effects of specific training on various muscle groups.

Study Results: Non-Recruited Muscles Atrophy

The study revealed a fascinating phenomenon: while most trained muscles increased in size by five to 20%, certain untrained muscles atrophied. This highlights the importance of engaging all muscle groups during training to avoid muscle loss. 

The primary drivers of muscle growth are muscle recruitment and external load, not nutrition or recovery.

D’Hulst acknowledges that individual responses to training can vary, and some individuals may be more susceptible to muscle loss than others. Tailoring workout plans will vary based on individual needs and responses.

Effect of Nutrition on Training Responses

Participants who consumed 24 calories per kilogram of body weight daily lost more muscle tissue than those who ate 36 calories per kilogram. The higher calorie and protein intake (over 1.6 grams per kilogram of body weight) ensures the body has the necessary raw materials to support muscle growth and repair.

D’Hulst stresses designing training programs that engage all muscle groups. He advocates for functional whole-body and compound movements like squats, deadlifts, pull-ups, and overhead presses. These exercises recruit multiple muscle groups simultaneously, minimizing the risk of muscle loss in non-recruited areas.

Key Takeaways

It’s possible to lose muscle tissue in non-recruited areas even on a regular training program. 

Prioritize exercises that work multiple muscle groups simultaneously to maximize muscle engagement and minimize the risk of atrophy.

Ensure a sufficiently high energy (36 kcal/kg of body weight) and protein (1.6 g/kg) intake to support muscle growth and repair. 

References

Aoyagi, Y., Tasaki, I., Okumura, J., & Muramatsu, T. (1988). Energy cost of whole-body protein synthesis measured in vivo in chicks. Comparative biochemistry and physiology. A, Comparative physiology, 91(4), 765–768. https://doi.org/10.1016/0300-9629(88)90962-0

VAN Vossel, K., Hardeel, J., VAN DER Stede, T., Cools, T., Vandecauter, J., Vanhaecke, L., Boone, J., Blemker, S. S., Lievens, E., & Derave, W. (2024). Evidence for Simultaneous Muscle Atrophy and Hypertrophy in Response to Resistance Training in Humans. Medicine and science in sports and exercise, 56(9), 1634–1643. https://doi.org/10.1249/MSS.0000000000003475

Featured image via shutterstock/rasamma

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