This meta-analysis explored whether males and females gain muscle in a similar way from resistance training. In healthy adults, males tended to gain more muscle in absolute terms - but when viewed relative to starting size, the results were remarkably similar. The findings suggest that similar training leads to comparable muscle growth, regardless of sex.
Overview
- What did they test? Researchers performed a Bayesian systematic review and meta-analysis of available studies to estimate differences in muscle hypertrophy - both absolute and relative changes - following resistance training in adult males and females. They also examined whether body region, measurement type, muscle fiber type, or prior training experience influenced the results.
- What did they find? From 2,199 articles initially identified, 30 met the inclusion criteria, although data could only be retrieved from 29 for full analysis. Absolute changes in muscle size slightly favored males, but no differences were found for relative changes. Absolute hypertrophy of the upper body also favored males.
- What does it mean for you? The main finding of this study adds to previous evidence that females have a similar ability to increase muscle size as males, with proportional improvements largely comparable between sexes. In practice, this suggests that similar training plans are likely to produce comparable hypertrophy outcomes for both males and females.
What’s The Problem?
Adult males and females differ in a range of physical and physiological traits. For example, males tend to be taller and heavier, and have greater baseline (untrained) levels of strength and muscle mass 1. They also typically have higher levels of anabolic hormones such as testosterone 2. Given these sex-based differences, it might be assumed that males also have a greater capacity to gain muscle mass through resistance training.
However, these differences don’t necessarily translate to differences in how muscle growth occurs. While supraphysiological levels of anabolic hormones (i.e., well above natural ranges) can enhance muscle gains 3, variations within normal physiological ranges are not always strongly associated with how much muscle is gained from training 4. This is likely because muscle hypertrophy is influenced by multiple mechanisms 5, many of which aren’t driven by hormone levels alone.
So while males may begin with greater muscle size, do they also experience greater gains in response to training? Many studies have explored this question by comparing muscle growth between males and females, or by including both sexes as participants. Previous meta-analyses have suggested similar relative gains in muscle size between sexes 6, although one only focused on older adults 7.
While current evidence leans toward males and females gaining muscle at similar rates from resistance training, it remains unclear whether meaningful differences exist - particularly when looking at absolute versus relative changes.
Purpose
This study aimed to investigate differences in absolute and relative changes in muscle hypertrophy following resistance training in healthy adult (18-45 years old) males and females, including specific impacts based on body region, muscle fiber type, and prior resistance training experience.
Hypothesis
The authors did not explicitly state a hypothesis.
