Here's another real deal old school guy. He has many videos out and here's one if you're an older/old guy getting back in shape. Another one about over training
Too much volume and frequency for me, although I did volume in that neighborhood until my mid-40s. Wouldn't dream of doing it now unless I was just going through the motions. (Thing is, I wonder if I even needed it then. Probably not.) Also, he said something about taking 30-45 seconds or so between sets. Even when I was in my 20s and 30s I never took such short breaks, let alone now (drop sets excepted).
The problem is there is no objective measure of recovery. Hell, there ain't even a definition. So, we are left to ourselves. Everyday workouts, not even if you are juicing to the max. Every other day? Probably too much for juicers & naturals too. Every third day. Still feels like too much, right, especially working out hard. Every fourth day? No we arte gettining somewhere. PROBABLY, too much. especially if every set is to absolute failure. Every two weeks? That's probably out the outer, but can't be dismissed. run a marathon, need more thatn two weeks. might need two months, which most people in the gym are running a marathon so to speak because they want to get big, quick. So, where do we find ourselves, les than twice per week but more than once every two weeks??
I think its also important to consider what your goals are. If you train not fully recovered this will increase your recovery capacity and also your threshold for how much volume you can tolerate without burning out. Our bodies are not as fragile as some fitness people will have you believe. There was a study I read where they tested people with squats every day and these were trained athletes. They were extremely fatigued and mentally drained but they were still able to set P.R's when push came to shove. https://shreddedbyscience.com/study-spotlight-squat-every-day-study/ There was another study where they took a Norwegian power lifting team and had kept volume the same but some did it in 1 or 2 sessions per week and others in 4-5 and the people who had more frequency had far better results. I dont have the link for this but you can find it.
Where is the evidence against it? If you're breaking down the muscle again before it has a chance to recover, let alone overcompensate, what is the expectation?
The idea behind hitting muscles every couple of days is that it keeps protein synthesis elevated in natural trainees. The body building split where you blast each muscle and let it recover for a week is good for people who are enhanced because they have elevated protein synthesis due to the extra testosterone so its fine to just blast yourself and then not work the same muscle again for 7 days. For a natural person you want to be hitting each muscle group 2-3 times a week. With more moderate volume / intensity. There is so much research and science to back this, you just have to google.
Yeah, but are they in it for the long haul, or just the next competition and then they take time off for full and proper recovery? Not a rhetorical question. Also, it's cool to use examples of genetic anomalies, but how many of us can relate? Just because those who are drawn to a competitive activity where they have a genetic advantage, which would likely include superior recovery ability, doesn't mean that it's necessarily the best approach for the majority of folks who are not on the far right of the bell curve.
The evidence against it is the overwhelming majority of people in the gym who are going multiple times per week and still making gains. What do you think the breakdown is between those that are in the gym 3-5 times weekly as opposed to those that are in the gym once every 7-10 days? I asking and I don't actually know, but based on casual observation the majority of people are in the gym a hell of a lot more than you're suggesting. Not that isn't working for you, obviously it is, but mainstream, I just ain't seeing it. And again, these more frequent gym goers are making gains.
Making gains is all about progressive overload... you need add weight or reps or lower the rest time between sets. What ever workout schedule allows this for you personally is the optimum one. If you are beginner its best to just stick to something cookie cutter but for someone experienced who knows their body, I think its really fun to experiment with different protocols and see which ones make you the most excited and give you the best results.