Equal Gains? A Meta-Analysis of Muscle Hypertrophy in Males and Females
Exploring sex differences in absolute and relative changes in muscle size following resistance training.
The study titled "Sex Differences in Absolute and Relative Changes in Muscle Size following Resistance Training in Healthy Adults: A Systematic Review with Bayesian Meta-Analysis" investigates how muscle hypertrophy varies between males and females in response to resistance training.
By analysing data from 29 studies, the research aims to clarify whether biological differences influence absolute and relative changes in muscle size and how factors such as muscle measurement methods, body regions, and training experience affect these outcomes. This comprehensive approach enhances our understanding of sex-related differences in muscle growth and informs future training strategies for both genders.
Key Points
Purpose: The study aimed to investigate the differences in absolute and relative changes in muscle size following resistance training (RT) between males and females. It also assessed whether factors like muscle size measurement methods, body regions, muscle fiber types, and RT experience influenced these outcomes.
Methodology:
A systematic review and Bayesian meta-analysis were conducted.
Of the 2,720 screened studies, 29 were included, comprising data from 1,278 males and 1,537 females aged 18-50.
The analysis focused on absolute changes (raw increase in muscle size) and relative changes (percentage increase from baseline).
Findings:
Absolute Muscle Size: Males showed a slight advantage in absolute increases in muscle size, with a standardised mean difference (SMD) of 0.19 (95% HDI: 0.11 to 0.28).
Relative Muscle Size: No significant difference was found between sexes for relative increases in muscle size, with an exponentiated percentage change of InRR at 0.69% (95% HDI: -1.50% to 2.88%).
Body Region Specificity: Males had greater absolute hypertrophy in upper-body regions, but not lower-body regions.
Muscle Fiber Type: Type I fiber hypertrophy favoured males slightly, while Type II fiber hypertrophy showed no significant differences between sexes.
Related
Practical Takeaways
Hypertrophy Potential: Females possess a similar potential for muscle hypertrophy as males when considering relative increases from baseline measurements. This finding underscores the importance of focusing on relative changes rather than absolute changes when evaluating training outcomes across sexes.
Training Implications: The results suggest that training programs can be designed without bias towards one sex regarding expected hypertrophic outcomes, particularly when assessing relative gains.
Future Research Directions: The study highlights the need for further investigation into the influence of muscle fiber types and other biological factors on hypertrophy across different populations and training experiences.
Conclusion
This systematic review with Bayesian meta-analysis provides valuable insights into sex differences in muscle hypertrophy following resistance training. While males exhibit greater absolute increases in muscle size, females demonstrate comparable relative gains, indicating that both sexes can achieve significant hypertrophic adaptations through resistance training. The findings encourage a nuanced understanding of muscle growth that transcends traditional gender stereotypes in strength training contexts.
Reference
Refalo, M., Fyfe, J., Gallagher, I., & Hamiliton, L. (2024, January 15). Biological Sex Differences in Absolute and Relative Changes in Muscle Size following Resistance Training in Healthy Adults: A Systematic Review with Meta-Analysis. Retrieved from osf.io/trz3y