My arms didn't grow for two years. Not because I wasn't training them. Because my split was working against me.
Back in high school I ran a standard Push Pull Legs. It's the default recommendation and it works fine for general training. But here's what nobody tells you about PPL: your arms are cooked before you ever isolate them. You just crushed heavy bench and overhead press on push day. Now you're supposed to grow your triceps? They're already fried. Same thing on pull day. Heavy rows and pulldowns torch your biceps before you even pick up a curl bar.
I was doing the work. My arms just never got the priority they needed.
So I changed the split. Chest, biceps, and shoulders. Back and triceps. Legs.
That alone blew my arms up. Biceps got a full session paired with chest where they aren't pre-fatigued. Triceps got the same treatment on back day. For the first time they were getting hit fresh with real intensity instead of getting leftover effort at the end of a session.
But my shoulders still weren't where I wanted them. Even with their own slot on chest and bi day they were getting squeezed in after two muscle groups that already took most of my energy. So I pulled them out and gave them their own day. Chest and biceps. Back and triceps. Legs. Shoulders. Another weak point solved by restructuring, not by adding more exercises or more sets.
But it didn't stop there. I started looking at specific muscles within those groups. My side delts weren't growing. My brachialis wasn't giving me the arm width I wanted. These are small muscles. They recover fast. So I started working side delts into my chest and bi day and brachialis into my leg day. That puts them on roughly an every-other-day frequency which is exactly what smaller muscles can handle.
Here's the principle behind all of this.
There is no perfect split. There's only the split that addresses what your physique actually needs right now. And that changes over time.
A few things to keep in mind when you build yours:
If something is a weak point, give it more frequency. Two to three days a week on a lagging body part is not overkill if you manage volume correctly. Smaller muscles recover faster than big ones. Your side delts don't need the same rest as your quads. Train weak points early in the session. You only have so much energy and systemic fatigue is real. Whatever you hit last is getting your worst effort. Stop running a split just because someone on the internet told you it's optimal. PPL is fine. Bro splits are fine. Upper lower is fine. None of them are built for your specific weak points out of the box.
The guys who actually change their physique are the ones who stop following templates and start engineering their training around what they need to fix. Look in the mirror. Be honest about what's lagging. Then build your week around fixing it.
Your split is a tool. Customize it or it's just a schedule.
-Zach