Key Takeaways on Strength Training for Muscle Growth
- A new 2025 study shows that strength training for muscle growth leads to very strong correlations between increases in muscle size and strength.
- The research found that muscle growth (hypertrophy) contributed more than five times as much to strength gains as neuromuscular activation, based on standardized regression coefficients.
- This new evidence challenges the long-standing idea that strength and size are separate goals — proving they are closely interconnected adaptations. Why Strength Training for Muscle Growth Matters
You’ve probably heard it before: “I’m a bodybuilder, not a powerlifter.” That old saying implies that building muscle and building strength are two different things. But new muscle growth science is showing that they’re actually two sides of the same coin.
A 2025 study published in Medicine & Science in Sports & Exercise by Marques et al. revealed powerful evidence that strength training for muscle growth leads to strength and hypertrophy developing together — not apart.4
Titled “Muscle Growth Is Very Strongly Correlated with Strength Gains after Lower Body Resistance Training: New Insight from Within-Participant Associations,” the study demonstrates that muscle growth plays a dominant role in driving strength increases in untrained individuals.
This finding challenges the long-held belief that “you can get stronger without getting bigger.” According to this new data, muscle growth and strength almost always rise together — at least within the same person over time.
Review of the Literature: Does Muscle Growth Correlate with Strength Gains?
The question of does muscle growth correlate with strength gains has been around for decades. Early studies by Moritani and DeVries (1979) found that strength gains early in a training program mostly come from neural adaptations — your brain and nervous system learning to better activate muscle fibers.1
But as training continues, strength training for muscle growth begins to show its true power. Later studies reveal that once those early neural gains plateau, muscle hypertrophy (growth in muscle fiber size) takes over as the main driver of strength increases.2,3
Until recently, the relationship between strength and hypertrophy seemed “moderate.” But that’s because most studies compared one person to another — what scientists call between-subject analysis.
Until recently, most studies suggested only a moderate correlation between hypertrophy and strength. However, that was largely because many compared different people — a “between-subject” approach.
The Marques et al. study (2025) took a different route. Instead of comparing different people, they tracked the same individuals over time, using advanced within-participant models. This allowed researchers to isolate the true relationship between how much someone’s muscles grew and how much stronger they became through strength training for muscle growth.
The result? The correlation between muscle growth and strength was exceptionally strong (r ≈ 0.9) — much higher than previously reported.
Results: The Power of Strength Training for Muscle Growth
In the 15-week study, 39 healthy young men trained their lower bodies three times per week. The workouts emphasized strength training for muscle growth, particularly exercises that targeted the quadriceps (like leg extensions and squats).
Researchers measured:
Muscle strength — using both isometric maximum voluntary torque (how much force you can produce when pushing against an immovable object) and one-repetition max (the heaviest weight you can lift once).
Muscle growth — by MRI scans that accurately measured quadriceps muscle volume.
Neuromuscular activation — by surface electromyography (sEMG), which measures how strongly the brain activates the muscle.
Here’s what they discovered:
The correlation between muscle growth and strength gain was nearly perfect (r ≈ 0.9).
Muscle growth explained over five times more variance in strength gains than neuromuscular activation (standardized beta coefficients 0.88-0.94 vs. 0.13-0.17).
This means strength training works not only because of better coordination or neural learning, but also because larger muscles produce more force.
Rethinking How Muscle Growth and Strength Work Together
So, does muscle growth correlate with strength gains? The evidence says yes — especially in untrained individuals.
This study shows that muscle hypertrophy is not just aesthetic; it is a key mechanical factor in strength development. When muscles grow, they gain more contractile proteins — the “engines” that produce force.
While neural adaptations dominate early in training, they tend to plateau after the first few weeks, at which point hypertrophy becomes the major driver of continued strength increases.
In practical terms: to keep getting stronger, your muscles need to grow.
This evidence also challenges the old-school mindset that separates “training for size” from “training for strength.” Although certain training methods can emphasize one adaptation over the other, both share common physiological foundations.
Practical Applications: How to Apply Strength Training for Muscle Growth
Here’s how you can use these findings in your own training:
Stop Treating Size and Strength as Mutually Exclusive
You don’t need to choose between being strong or being big. The latest research shows they develop together, especially during well-designed resistance training programs.
Focus on Progressive Overload
Gradually increase the resistance you lift — even small jumps (1–5 lb or 0.5–2 kg) drive both hypertrophy and strength adaptation.
Balance Intensity and Volume
Heavy weights build neural efficiency and strength, while higher training volume stimulates hypertrophy. Combining both creates optimal conditions for long-term progress.
Track Strength Metrics, Not Just Appearance
If your strength numbers are rising, it’s a strong indicator that your muscles are growing, even before visual changes appear.
Conclusion: Size Is Strength
The Marques et al. (2025) study finally bridges the gap between muscle size and strength, revealing that strength training for muscle growth is the foundation for long-term progress.
The data is clear: muscle growthr isn’t just cosmetic — it’s functional. The more muscle you have, the stronger you become.
So next time someone says, “I’m training for size, not strength,” remind them that muscle growth science says otherwise. Bigger muscles are stronger muscles.
In the end, size and strength aren’t rivals — they’re partners.
References
1 Moritani, T. & deVries, H. A. Neural factors versus hypertrophy in the time course of muscle strength gain. Am J Phys Med 58, 115-130 (1979).
2 Erskine, R. M., Fletcher, G. & Folland, J. P. The contribution of muscle hypertrophy to strength changes following resistance training. Eur J Appl Physiol 114, 1239-1249 (2014). https://doi.org/10.1007/s00421-014-2855-4
3 Vigotsky, A. D., Schoenfeld, B. J., Than, C. & Brown, J. M. Methods matter: the relationship between strength and hypertrophy depends on methods of measurement and analysis. PeerJ 6, e5071 (2018). https://doi.org/10.7717/peerj.5071
4. Marques, Elisa A.1,2,3; Balshaw, Tom G.1; Funnell, Mark P.1,4; McDermott, Emmet J.5; Maeo, Sumiaki1,6; James, Lewis J.1,7; Folland, Jonathan P.1,7. 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 ():10.1249/MSS.0000000000003819, July 18, 2025. | DOI: 10.1249/MSS.0000000000003819
