Scientific Programme
Plenary Session
PS-PL02 - Mechanisms of Human Skeletal Muscle Hypertrophy: Sorting the Wheat from the Chaff
Date: 03.07.2025, Time: 11:30 - 12:45, Session Room: Anfiteatro
Description
This symposium will focus on the mechanisms behind human skeletal muscle hypertrophy induced by mechanical overload, primarily through resistance training. Hypertrophy is a critical factor for improving performance in athletes and preventing muscle loss due to aging or disease. The symposium will explore key signalling pathways, including the mammalian target of rapamycin complex 1 (mTORC1) pathway, which plays a crucial role in promoting muscle protein synthesis following resistance training. Additionally, it will cover the role of satellite cells and their contribution to muscle repair and growth, along with insights into omic factors that influence hypertrophy outcomes. This symposium is particularly relevant for members of the ECSS, who are involved in enhancing athletic performance and maintaining muscle health in various populations, including athletes and older adults. Understanding the cellular and molecular underpinnings of muscle hypertrophy provides invaluable insights for optimizing training protocols, rehabilitation strategies, and nutritional interventions. The symposium is designed for researchers, sports scientists, coaches, and health professionals interested in the physiological adaptations to resistance training. It will appeal to those focused on enhancing athletic performance, understanding muscle aging, and developing effective strategies for muscle rehabilitation and growth in all populations.
Chair(s)
Jatin Burniston
Liverpool John Moores University, Research Institute for Sport and Exercise Sciences
United Kingdom
Mechanisms Underpinning Human Hypertrophy: From Application to OMICs
Human skeletal muscle hypertrophy is a complex and multi-faceted process primarily driven by mechanical overload facilitated through resistance exercise. This talk will investigate the current understanding of the mechanisms that underpin hypertrophy and strength gain with resistance training (RT). A key focus will be on the role of external factors – protein, resistance training variables, and certain supplements – used in combination with RT to shift the balance towards net protein accretion, leading to hypertrophy and the development of strength. This talk will also address practical applications, discussing how specific training variables—such as load, frequency, and volume—modulate the hypertrophic response. These variables directly influence intracellular signalling cascades, demonstrating the interaction between applied training methods and the underlying molecular mechanisms. This knowledge is essential for designing optimal training programs for athletes and older adults looking to maintain muscle mass and strength. This presentation is particularly relevant for the ECSS community, which focuses on improving athletic performance and physical health. Understanding the biological basis of hypertrophy allows for more effective training prescriptions, rehabilitation strategies, and nutritional interventions. It also opens the door for personalized approaches to muscle growth, making it highly applicable to both sports scientists and clinical practitioners. By combining traditional knowledge with the latest in an understanding of hypertrophy mechanisms, this talk will offer a comprehensive overview of skeletal muscle hypertrophy and strength gains. Attendees will gain a deeper understanding of both the applied and underpinning mechanisms driving muscle growth, bridging the gap between practical training techniques and advanced scientific discovery.
Speaker B
Abigail Mackey
University of Copenhagen, and Bispebjerg Hospital, Department of Clinical Medicine, and Institute of Sports Medicine Copenhagen
Denmark
Read CVECSS Rimini 2025: PS-PL02
Don’t forget, hypertrophy is not just for the beach - the structural and cellular drivers and facilitators of hypertrophy
In addition to protein turnover measures and OMICS type data, the cellular and structural aspects of the entire muscle-tendon unit are key to understanding the full picture of mechanisms driving skeletal muscle hypertrophy. This talk will build on Professor Phillips’ comprehensive coverage of the topic and delve into: 1. Changes in whole muscle architecture 2. Myofibre and myofibril addition 3. The role of muscle damage 4. The key cell types facilitating adaptation and their memories 5. Hypertrophy is not just for the beach Skeletal muscle hypertrophy is defined as increases in the cross-sectional area (CSA) of a single muscle or group of muscles. However, load-induced growth of muscle alters muscle architecture, including pennation angle and muscle length, which necessitate adaptation of the muscle extracellular matrix and its attachment to the tendon for safe and effective transmission of forces. Activity of many cell types is therefore required. Hyperplasia, the addition of myofibres, remains the stuff of legend as a key factor in reaching extreme muscle hypertrophy. This talk will examine the evidence for and against hyperplasia as well as the potential cellular mechanisms facilitating this feat in the adult. Zooming in on individual myofibres, changes in myofibril size and number during hypertrophy will also be considered. Myofibre damage will also be explored – from the point of view of mechanism or consequence of load-driven hypertrophy. As the increased protein synthesis translates into larger myofibres, extra myonuclei are required to sustain further growth. Elegant animal models have shown that satellite cells are the sole source of these new myonuclei, and it is becoming increasingly clear that other cell types in the muscle interact with satellite cells to regulate adaptation of the muscle as a whole. In this context, immune cells, fibroblasts, tenocytes and the motoneurone itself will be considered. Lastly, hypertrophy is not just for the beach. This talk will end by putting hypertrophy into the perspective of healthspan and lifespan. Building muscle mass is possible at any stage of life. However decades of inactivity may lead to accelerated loss of myofibres. Depending on whether new myofibres can be added in the adult state, myofibre loss may be a permanent event and therefore a severe limitation to the capacity to develop hypertrophy later in life and even in midlife. Furthermore, cells remember previous events, so building up “positive memories” by mechanical loading throughout life may provide a valuable resource for rebuilding muscle lost during periods of forced inactivity such as illness or injury. Attendees of this session will be presented with evidence for and against the fundamental mechanisms driving, facilitating and remembering hypertrophy, as well as the broader perspectives for muscle health.