The Data Doesn't Lie: Train Each Muscle Twice a Week

A common training split at the beginner to intermediate level of training is the "bro split." The bro split means you train each body part once per week; typically a leg day, back day, arm day, etc.

Some people stick with this training style their entire life, while others move on to other splits like push/pull/legs or full body training.

Researchers set out to determine how much frequency matters when it comes to building muscle. In other words, how often you are training the muscle. The great thing about this particular analysis was that it equated for volume. If you train a muscle more often, then over time there's a good chance you'll see more growth. But the researchers didn't want that to be a factor, so volume was the same amongst all studies included.

They found that training each muscle group twice per week produced about 65% more muscle growth than training it once per week (6.8% vs 3.7% average muscle gain), and this held true even when total weekly training volume was kept the same across groups.

With that said, you may think "if training twice per week is better than once, then three times must be better than two." This is a common if some is good, more is better fitness ideology. But the research does not necessarily support this. There wasn't enough data to say definitively whether a third weekly session adds more benefit.

This study is often cited by advocates of high frequency training, but one criticism is the way they measured muscle growth. This was a meta-analysis of 10 studies, and many of the studies used indirect measurements (limb circumference, body composition scans) rather than precise imaging of individual muscles.

So, what does this mean for your training? If you are currently running a bro split and your primary goal is building muscle, the evidence suggests you are likely leaving gains on the table. Restructuring your program to hit each muscle group twice per week may produce meaningfully better results without requiring you to do any additional work overall. If higher frequency training allows you to do more volume anyway, then that is probably an advantage as well.

That said, this does not mean the bro split is useless. It still builds muscle, and for some people it may be the most sustainable and enjoyable way to train. Consistency will always trump the perfectly optimized program. Many people get lost in the weeds trying to make everything optimal. In reality, a bro split can take you a long way.

As with most things in exercise science, this research is a useful guide rather than a definitive rulebook. The studies were short, the measurement tools were imperfect, and individual responses to training vary widely. What works best for you may take some personal experimentation. But if the goal is maximizing muscle growth, training each muscle twice a week is a reasonable and evidence-backed place to start.

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This story was originally published May 29, 2026 at 10:42 AM.