Intuitively, we understand that stronger individuals have larger muscles, and this has been supported by research showing inter-individual differences in muscle strength are mostly explained by differences in muscle volume. However, when we try to unpack the specific contribution of different neuromuscular changes (e.g., muscle size and muscle activation) to changes in muscle strength there are often relatively modest relationships reported. Several issues could help explain these fairly modest relationships between changes muscle size/activation and changes in muscle strength, such as the duration of the resistance training being insufficient (i.e., <12weeks) to bring about large increases in muscle size; the use of low-resolution measurements of muscle size; single measurements of strength performed pre and post training; and finally, the reliance on between participant analysis which may lack sensitivity to capture intra-individual changes in muscle strength, size and activation. This study aimed to assess the intra-individual relationship using novel repeated measure correlational analysis between changes in both muscle volume (using high resolution magnetic resonance imaging) and muscle activation with changes in isometric and isoinertial strength (duplicate measures at pre and post training) in males following 15 weeks of supervised lower body resistance training. It was found that changes in muscle volume (r=0.89-0.92) were strongly related to changes in muscle strength, which is much greater than has been previously reported. Whereas more modest relationships were found between changes in muscle strength and muscle activation (r=0.56-0.58). These findings help to provide greater clarity on the contribution of changes in muscle size and muscle activation with muscle strength following resistance training sustained for 15 weeks.
Marques, Elisa A., Balshaw, Tom G., Funnell, Mark P., McDermott, Emmet J., Maeo, Sumiaki., James, Lewis J., Folland, Jonathan P. (2025) Muscle Growth Is Very Strongly Correlated with Strength Gains after Lower Body Resistance Training: New Insight from Within-Participant Associations. Medicine & Science in Sports & Exercise | DOI: 10.1249/MSS.0000000000003819 Medicine & Science in Sports & Exercise
Dr. Emmet Mc Dermott, is a University Teacher in Sport and Exercise Science, in the Department of Physical Education and Sport Sciences, UL. Emmet initially attended the Institute of Technology Carlow, where in 2016 he graduated with a BSc in Sport Science. In 2017, Emmet graduated with MSc in Exercise Physiology from Loughborough University and remained in Loughborough to complete his PhD in Neuromuscular Function under the guidance of Prof Jonathan Folland, graduating in 2022. Emmet has previously held roles as an assistant lecturer role in Sport Science at the South-East Technological University, and lecturer in Sports Engineering at Nottingham Trent University.
Contact: emmet.mcdermott@ul.ie.
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