Women build muscle at the same relative rate as men

Whether men and women respond differently to lifting weights is one of the longest running arguments in exercise science. Muscle hypertrophy may be influenced by biological differences between the sexes, and plenty of training advice is still written on the assumption that women gain less. What previous work had not settled is whether any male advantage reflects a genuinely stronger response to training or simply a larger starting point. This review set out to compare both absolute and relative changes in muscle size between the sexes, and to test whether the answer shifts depending on how muscle is measured, which body region is assessed, muscle fibre type, or training experience.

The researchers conducted a systematic review with a Bayesian meta-analysis, screening 2,720 studies and including 29 in the final statistical analysis. Eligible studies enrolled healthy adults aged 18 to 45 in which male and female participants completed the same resistance training intervention, with muscle size measured before and after the programme. The team estimated standardised mean differences for absolute change, a response ratio expressed as a percentage for relative change, and the probability that each effect ran in a given direction. They also checked whether the measure of muscle size, the body region assessed, muscle fibre type and resistance training experience moderated the results.

Absolute increases in muscle size slightly favoured males, with a standardised mean difference of 0.19, and the analysis was essentially certain about the direction of that small effect. Relative increases from baseline, however, were similar between the sexes, with an estimated difference of just 0.69% and an interval running from minus 1.50% to 2.88%, comfortably spanning zero. The male advantage in absolute terms appeared in upper-body regions but not lower-body regions. Type I muscle fibre hypertrophy slightly favoured males, while Type II fibre growth was similar between sexes. Results were minimally influenced by how muscle size was measured and were not influenced by participants' training experience.

The finding strengthens an emerging consensus that females have a similar potential for muscle hypertrophy as males, particularly once gains are expressed relative to starting muscle size. It complicates the simpler story that men are uniformly better responders, narrowing any genuine male advantage to absolute upper-body growth and possibly Type I fibres. The authors flag where the evidence remains thin: highly trained participants, since the included studies did not settle how the pattern plays out in that group, and fibre type specific hypertrophy, where the data are limited. Future research in those areas could refine the detail without necessarily changing the headline conclusion.

If you are a woman lifting weights, this is a reason to expect muscle growth at much the same relative rate as a man following the same programme. The male edge appeared only in absolute size, and mainly in the upper body; measured against each person's own starting point, the sexes matched. For anyone comparing progress between people, relative change from baseline looks like the fairer yardstick. And because training experience did not alter the pattern in this analysis, the finding is relevant whether someone is picking up a barbell for the first time or has trained for years.