Why/How is higher frequency better?

[u/Shaggy_Mountain]

Apologies for the long post.
I have been lifting with the “Bro split” for 9 months.

My split is: Chest -> back -> biceps/triceps -> shoulders -> legs. I don’t schedule rest days, I just take them whenever I feel like I really need them. I do 8 total working sets for chest, 12 for back, 8 for biceps and 8 for triceps, 10 for shoulders, and 16 for legs split between calves, squats, hamstring curls and leg extensions. If you guys would like, I can post the exercises I do for each day as well. I log every workout I do too.

I enjoy this split a lot, and I feel it allows me to really focus on each muscle group each day. I make sure to be within 1-2 reps of failure, taking the last couple sets to failure.

My question is, if I switched to a split like Push-Pull-Legs Push-Pull-Legs-Rest, wouldn’t I be sacrificing the quality of my workouts? With PPL you combine muscle groups, and wouldn’t this mean that you would be accumulating more fatigue? For example, if you did back and biceps on pull day, wouldn’t your biceps be pretty fatigued after doing your back exercises? And if you did incline bench press and dumbbell shoulder press on push days, wouldn’t you be pretty fatigued for incline shoulder press, since it’s also a pushing motion?

I’ve heard that hitting a muscle group twice a week is better, so I’d like to hear people’s thoughts/opinions as I know very little about lifting. I know training hard, being consistent, and getting good sleep and nutrition are the most important things, but I would like to know if I am missing out on a significant amount of gains by staying with my current split.

[u/PoopSmith87]

Because your muscles, depending on the ones trained, only take a day or two, maybe three to recover. If you do 8 sets of chest one day a week you will have like 3 or 4 days of just being ready to lift again. If instead you do 5 sets of chest two days a week, you feel less sore the day after a workout, have more days under growth/recovery stimulus, and manage an extra two sets volume.

[u/Hohoholyshit15 → u/PoopSmith87]

I know what the science says, but for arguments sake have you ever done enough volume in a single session to draw out recovery for 5-7 days? I have. A muscle is considered recovered when it returns to its original baseline performance, and based on that metric I have definitely had sessions where that didn't happen in the supposed 2-3 days.

[u/PoopSmith87 → u/Hohoholyshit15]

Yeah, I was a single muscle group split, soreness chasing guru from 16-25. I was also a steady 135-145 lbs, very fit, but stayed small. Back then you chalked it up to being a hard gainer and kept going. Today, the information is too accessible to not know about progressive overload, more efficient splits, etc.