For young women, more lifting sessions means more muscle

Much of the foundational resistance training research was conducted in men, leaving open questions about how reliably the findings transfer to women and which programming variables matter most for them. Healthy young women are increasingly lifting for strength, physique and long-term health, so pinning down what resistance training actually delivers for this group, and what moderates the size of those gains, has real practical value. This review set out to quantify the effects of resistance-based programmes on body fat percentage, lean mass, hypertrophy, strength and power in healthy women aged 18 to 35, and to test whether sessions, weekly volume or intensity moderated the results.

The authors systematically searched 7 databases from inception to May 2022 for randomised controlled trials of resistance-based exercise programmes in healthy young women aged between 18 and 35. Forty articles covering 1,312 participants met the criteria. They pooled outcomes with a 3-level mixed-effects meta-analysis model and then ran meta-regression models testing whether the number of sessions, weekly volume and training intensity were associated with the size of improvements. Standard significance was set at 0.05, with values between 0.05 and 0.10 also considered for potential moderators.

Resistance training improved muscle strength by a large 1.2 SMD and lean mass or muscle hypertrophy by 0.4 SMD, both statistically significant. Body fat percentage improved by -0.4 SMD and muscle power or rapid force by 0.6 SMD. On the moderators, a higher number of sessions was significantly associated with greater lean mass and hypertrophy changes, while a higher weekly volume approached but did not reach statistical significance for moderating strength gains. Notably, improvements in power and rapid force appeared irrespective of how the programme was prescribed.

This pooling confirms in women specifically what the broader literature has long suggested: resistance training builds strength substantially, adds lean mass more modestly, and improves body composition and power. The dose-response signal, where more sessions meant more muscle, echoes the volume relationships reported in mixed and male samples, extending them to a population that has historically been under-studied. Open questions remain about which intensities and volumes are optimal rather than merely better, since the weekly volume link to strength fell just short of significance and the included programmes varied considerably.

For women between 18 and 35 who lift or are considering it, this is strong evidence the returns are real across the board: strength most of all, with meaningful gains in muscle, power and body composition. The finding that session count moderated muscle gains is a reason to think consistency and accumulated training, rather than any single clever programme detail, drives hypertrophy. And the fact that power improved regardless of prescription suggests newcomers need not agonise over programme design to get faster and more explosive early on.