Do Men Grow More Muscle Than Women?
New meta-analysis reveals sex differences in muscle growth.
Do men and women really build muscle differently through weight training, and how is this measured? This systematic review with Bayesian meta-analysis investigated whether biological sex affects muscle growth from resistance training and whether the answer depends on how we measure that growth.
Overview
This comprehensive meta-analysis examined 29 studies including 1,278 male and 1,537 female participants aged 18–45 years to determine whether sex differences exist in muscle growth following resistance training. The researchers distinguished between absolute changes (raw increases in muscle size) and relative changes (percentage increases from baseline), a critical distinction that previous research overlooked.
Aim
The aim was to investigate differences in both absolute and relative changes in muscle size following resistance training between males and females. Secondary aims examined whether factors such as measurement methods, body region assessed, muscle fiber type, and training experience moderated any sex differences in muscle hypertrophy outcomes.
Methods
The researchers conducted a systematic review following PRISMA guidelines, searching PubMed, SCOPUS, and SPORTDiscus databases through August 2024. They included studies where male and female participants aged 18–45 years completed identical resistance training interventions.
From 2,720 initially screened studies, 29 met the inclusion criteria and were analysed using Bayesian statistical methods. The analysis included 68 muscle hypertrophy outcomes measured through various methods, including MRI, ultrasound, CT scans, muscle biopsies, and body composition assessments.
Training interventions ranged from 6 to 24 weeks with a mean duration of 11 weeks. The researchers calculated standardised mean differences (SMD) for absolute changes and log response ratios converted to percentage changes for relative changes.
Results
Main Findings
Absolute muscle size increases slightly favoured males with an SMD of 0.19, representing a 100% probability that males experienced greater absolute hypertrophy. However, relative increases in muscle size were similar between sexes, with a percentage change of 0.69% indicating no meaningful difference when accounting for baseline muscle size.
Body Region Analysis
Upper-body absolute muscle growth showed a greater sex difference (SMD = 0.30) compared to lower-body regions (SMD = 0.17). However, relative changes remained similar between sexes regardless of the body region assessed.
Muscle Fiber Type Findings
Type I muscle fiber hypertrophy showed a greater than 90% probability of favouring males with an absolute SMD of 0.39 and a relative change of 12.7%. Conversely, Type II muscle fiber hypertrophy was similar between sexes, with a relative change of -2.29% slightly favouring females (though with considerable uncertainty).
Training Experience
Whether participants were resistance-trained or untrained did not influence sex differences in absolute or relative muscle hypertrophy. Resistance-trained participants showed an SMD of 0.20 compared to 0.19 for untrained participants.
Measurement Methods
Sex differences were more evident with direct measures (muscle CSA, thickness, volume, and fiber CSA) versus indirect measures like lean mass assessed via DXA or BIA. However, relative changes remained similar across all measurement methods.
Practical Takeaways
Women can build muscle just as effectively as men when considering percentage gains from baseline—your smaller starting point doesn’t mean worse growth potential.
Train both upper and lower body consistently—while men showed slightly greater absolute gains in upper-body muscles, relative growth rates were comparable, meaning women shouldn’t neglect upper-body training.
Training experience doesn’t change the equation—whether you’re a beginner or experienced lifter, sex differences in hypertrophy remain consistent, so program structure can be similar for both sexes.
Focus on progressive overload principles—since the study showed similar relative gains between sexes across various protocols (6-24 weeks, different volumes and intensities), fundamental training principles matter more than sex-specific programming.
Consider individual factors over sex—the researchers emphasise that programming should be based on individual goals, preferences, stress tolerance, and enjoyment rather than biological sex.
Key Takeaways
This rigorous meta-analysis of 29 studies provides strong evidence that females have similar muscle-building potential as males when accounting for baseline differences in muscle size. While males experience slightly greater absolute increases (0.19 SMD), this advantage disappears when examining relative percentage changes (0.69% difference).
These findings challenge traditional assumptions about sex differences in hypertrophy, suggesting that factors beyond sex-specific hormones, such as mechanical tension, metabolic stress, and anabolic signalling, play primary roles in muscle growth. Interestingly, possible sex-specific differences emerged in fiber-type hypertrophy, with males showing greater Type I fiber growth, though these findings require cautious interpretation due to measurement variability.
For practical application, resistance training programs can follow similar structures for males and females across all training levels, with individualisation based on goals and personal factors rather than biological sex. The consistency of findings across different measurement methods, body regions (with noted upper-body differences), and training statuses strengthens these conclusions.
Reference
Refalo MC, Nuckols G, Galpin AJ, Gallagher IJ, Hamilton DL, Fyfe JJ. 2025. Sex differences in absolute and relative changes in muscle size following resistance training in healthy adults: a systematic review with Bayesian meta-analysis. PeerJ 13:e19042 https://doi.org/10.7717/peerj.19042
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