How often should you train a muscle? Frequency matters less than total volume

How often should you hit each muscle to make it grow? The short answer that the best evidence now supports: often enough to fit your weekly sets in, and no particular number beyond that. Once you match the total work, training a muscle twice a week and three times a week produce about the same growth [s2]. Frequency is mostly a way to distribute volume, not a separate lever on it.

The 2016 answer: twice beat once

The question first got a clear meta-analytic answer in 2016, when Schoenfeld, Ogborn and Krieger pooled ten studies that directly compared different weekly training frequencies [s1]. Using a binary split of higher versus lower frequency, they found a significant effect on hypertrophy (P = 0.002): the higher-frequency conditions produced a larger effect size than the lower ones, 0.49 ± 0.08 against 0.30 ± 0.07 [s1]. Their conclusion, widely quoted since, was that on a volume-equated basis the major muscle groups should be trained at least twice a week to maximise growth [s1].

Crucially, most of those studies compared one session a week against two — and in several, the higher-frequency group also did more total sets. The authors were explicit that they could not reliably isolate session frequency when groups were matched for volume per muscle, because the sample of such studies was too small [s1]. The finding was real, but the mechanism it pointed to was ambiguous: was twice a week better because of the frequency, or because it packed in more work?

The 2019 answer: it was the volume

Three years later the same lead author revisited the question with a much larger evidence base — 25 studies — and a design built to separate the two [s2]. When weekly volume was equated, higher and lower frequencies produced no significant difference in muscle growth [s2]. The null held across the board: for direct measures of growth, in trained participants, and for the upper body and lower body analysed separately [s2].

There was one caveat in the other direction. Among studies that did not equate volume, a meta-regression favoured higher frequencies — but the authors described the difference in effect between training a muscle once and three-plus times a week as modest [s2]. In other words, more frequent training tends to look better mainly because it is a convenient way to accumulate more sets. Once the sets are held constant, the schedule stops mattering. Their conclusion was blunt: for a given training volume, individuals can choose a weekly frequency per muscle group based on personal preference [s2].

What it means for a training week

Read together, the two analyses tell a consistent story that has quietly become consensus. The thing that drives hypertrophy is how much hard weekly volume a muscle gets; frequency is the container you pour that volume into [s1][s2]. If you have, say, a dozen weekly sets planned for a muscle, spreading them across two or three sessions rather than cramming them into one is reasonable — not because the extra day is magic, but because smaller doses are easier to perform well and recover from. A muscle you train once a week has to absorb its entire weekly workload in a single session, and quality tends to fall away as fatigue mounts across it; splitting the same sets over two or three days keeps each one fresher. The 2016 "at least twice a week" guidance survives as a practical default, not a physiological rule [s1][s2].

The honest caveats

Both papers concern muscle size, not strength or skill, and both are built largely from short training studies in small groups [s1][s2]. Very high frequencies were sparsely studied, so this is not licence to train a muscle daily; recovery still bounds how much quality work you can do. And "volume-equated" is doing real work in the 2019 conclusion — the finding is that frequency does not add growth on top of a fixed amount of work, not that how you train never matters.

The useful takeaway is liberating rather than prescriptive. A reader juggling a schedule does not have to hit a magic number of sessions per muscle; they have to get their weekly sets done, with enough effort and recovery, in whatever split fits their life. That fits the wider hypertrophy picture, where total volume did more of the work than any single variable, and where proximity to failure nudges size but not strength.

Sources

1. [s1] Schoenfeld BJ, Ogborn D, Krieger JW. Effects of Resistance Training Frequency on Measures of Muscle Hypertrophy: A Systematic Review and Meta-Analysis. Sports Medicine, published online 21 April 2016. https://doi.org/10.1007/s40279-016-0543-8
2. [s2] Schoenfeld BJ, Grgic J, Krieger J. How many times per week should a muscle be trained to maximize muscle hypertrophy? A systematic review and meta-analysis of studies examining the effects of resistance training frequency. Journal of Sports Sciences, published online 17 December 2018. https://doi.org/10.1080/02640414.2018.1555906