The Bro Split Question
For decades, bodybuilders followed the classic split: chest on Monday, back on Tuesday, shoulders Wednesday, legs Thursday, arms Friday. Each muscle got hammered once per week with massive volume, then left to recover for seven days.
But is this actually optimal? Or are we leaving gains on the table by waiting a full week between training sessions for each muscle group?
What the Research Found
A 2016 meta-analysis published in Sports Medicine examined 10 studies comparing different training frequencies. The researchers controlled for total weekly volume, meaning they compared training a muscle once with 10 sets versus training it twice with 5 sets each session (same total work).
The results favored higher frequency:
- Training muscles twice per week produced significantly greater hypertrophy than once per week
- The difference was about 3.1% greater growth for higher frequency
- This effect held true even when total weekly volume was identical
The Science Behind Frequency
Why does training a muscle more often work better, even with the same total volume? The answer lies in protein synthesis.
After you train a muscle, protein synthesis (the process of building new muscle tissue) increases. But this elevation doesn't last forever. Research shows protein synthesis peaks around 24 hours post-workout and returns to baseline within 36-48 hours in trained individuals.
If you train chest on Monday and wait until the following Monday, you get about 2 days of elevated protein synthesis followed by 5 days at baseline. Train chest on Monday and Thursday, and you get two separate 2-day elevations, keeping the growth signal active for more of the week.
What This Means for Your Training
The research suggests restructuring how you think about workout splits:
Instead of: One muscle group per day, trained once weekly with high volume
Consider: Each muscle group trained 2-3 times per week with moderate volume per session
Frequency-Friendly Splits
Here are training splits that hit each muscle at least twice per week:
Upper/Lower Split (4 days):
- Monday: Upper body
- Tuesday: Lower body
- Thursday: Upper body
- Friday: Lower body
Push/Pull/Legs (6 days):
- Monday: Push (chest, shoulders, triceps)
- Tuesday: Pull (back, biceps)
- Wednesday: Legs
- Thursday: Push
- Friday: Pull
- Saturday: Legs
Full Body (3 days):
- Monday: Full body
- Wednesday: Full body
- Friday: Full body
But What About Recovery?
A common concern: "If I train chest Monday, won't it still be sore by Thursday?"
The key is volume distribution. If your weekly chest volume is 16 sets, you're not doing 16 sets on Monday and 16 more on Thursday. You're doing 8 sets each day. The per-session demand is lower, recovery is faster, and you can train the muscle again sooner.
Soreness itself isn't a reliable indicator of whether you can train a muscle. What matters is whether you can perform with good form and progressive overload. Most people find they can train a muscle again 48-72 hours later when volume is appropriately distributed.
Does Three Times Per Week Beat Twice?
The research is less clear on whether training each muscle three times weekly is better than twice. Some studies show additional benefit, others don't. The practical constraints also matter: fitting adequate volume for all muscle groups into a 3x weekly full body routine is challenging.
For most lifters, twice per week per muscle group is the sweet spot that balances growth stimulus with practicality.
The Bottom Line
Training each muscle once per week leaves gains on the table. The research supports hitting each muscle group at least twice weekly. If you're currently using a traditional bro split, consider switching to an upper/lower, push/pull/legs, or full body routine.
Your weekly volume can stay the same. You're just distributing it more effectively across the week to keep protein synthesis elevated longer and maximize muscle growth.
Reference
Schoenfeld BJ, Ogborn D, Krieger JW. Effects of Resistance Training Frequency on Measures of Muscle Hypertrophy: A Systematic Review and Meta-Analysis. Sports Med. 2016;46(11):1689-1697. PMID: 27102172