A long-standing question in exercise science has been whether strength improvements are primarily the result of increasing muscle size or the nervous system becoming more efficient at using existing muscle.
A new study from Loughborough University provides one of the clearest answers yet, showing that muscle growth plays the dominant role in building strength.
The Study
Published as a preprint in Medicine & Science in Sports & Exercise, the research examined how changes in muscle size and neuromuscular activation relate to strength gains following resistance training.
Unlike previous studies that often relied on cross-sectional comparisons, this study tracked changes within individual participants, offering a more precise understanding of how these factors contribute to strength development.
Methods
The study involved 39 healthy young men with no recent resistance training experience. Participants underwent a 15-week lower-body training program, performing leg extensions, leg curls, and leg presses three times per week.
Muscle growth in the quadriceps was measured using high-resolution MRI, while neuromuscular activation was assessed with surface EMG. Strength was evaluated using both isometric maximum voluntary torque and one-repetition maximum (1RM) testing before and after the training period.
Results
After 15 weeks, participants experienced an average 13% increase in quadriceps muscle volume, with corresponding strength gains of approximately 22% in isometric testing and 29% in 1RM performance. Muscle growth and strength improvements were closely linked on an individual level.
In contrast, increases in neuromuscular activation showed only moderate associations with strength gains. When analyzed together, muscle growth was found to be more than five times as predictive of strength improvements as neural adaptations.
Conclusion
The researchers concluded that “muscle growth is very strongly, and neuromuscular activation moderately, associated with strength gains after resistance training.” The findings suggest that for young, healthy men, increasing muscle mass is a primary driver of long-term strength development, whereas neural adaptations, while still important, play a secondary role.
Implications for Training
For those beyond the initial “newbie gains” phase—rapid strength increases largely due to neural adaptations—building muscle becomes essential for continued progress. Neural efficiency does contribute to strength, but its impact plateaus once most existing muscle fibers are recruited.
Therefore, maximizing strength gains requires focusing on progressive overload, adequate training volume and intensity, and sufficient recovery to stimulate muscle growth. For intermediate and advanced lifters, chasing bigger lifts ultimately means prioritizing bigger muscles.
YOU MAY ALSO LIKE
