I've been thinking about doing full body 4 or even 5 times a week.
Can this be optimal for muscle growth and endurance?
Training history 5 months of starting strength, hated it and tried Stronglifts and then Madcow for about a year.
Physical Fitness Stack Exchange is a question and answer site for physical fitness professionals, athletes, trainers, and those providing health-related needs. It only takes a minute to sign up.Sign up to join this community
My answer is a "Yes, as long as you don't plan to spend all 5 days in the gym, lifting heavy weights".
While in my opinion, a full body workout is the way to go for a novice, hitting the barbells 5 times a week may not be the most sensible choice. The average novice takes 24-72 hours to fully recover and supercompensate from an adequate training stimulus. Working out on five days a week leaves you with several rest periods at the very low end of this spectrum. This can work if you are in your early twenties, just started working out, and a bunch of other factors (genetics, nutrition, lifestyle,...) are playing in your favor. But for the average novice, this is not a sustainable rate. The maximum I'd recommend is a 3/4 days per week (i.e. every other day), or a 3 days per week regimen if you prefer to have your workouts always on the same weekdays.
However, this statement is just limited to weight training after an established program like Starting Strength. You can complement your strength training with days that focus on other qualities, generally speaking: aerobic fitness like swimming, anaerobic conditioning like HIIT,... have been proven to go well with classical strength training.
Most people would recommend Starting Strength as the go-to novice strength training program. Personally, I'd suggest to have a look into Johnny Pain's Greyskull Linear Progression (don't be repelled by the stupid name). It is an derivative of Starting Strength that tackles SS' biggest weaknesses, and comes up with many variations and "plug-ins" to customize your training regimen to your personal goals.
Edit: Well, after seeing the additional info you provided, you're clearly past the novice stage. Greyskull LP will be rather inappropriate for you.
A more appropriate advanced program would be Destroy the Opposition (Another stupid name, I know). It is a "sort of" full body 5-day regimen. It is strongly geared towards powerlifting, if that's your thing. Personally, I haven't tried it myself but heard only good things about it
If you are doing full body weight training then you should first try every other day, proceeding to three times a week once you find that you are not recovering fast enough, plus remember to take a rest or deload week every eight to ten weeks. This advice is all over the internet.
4-5 days a week means there will be some days you will be working the same muscles (all of them if full body!) consecutively, and I'm sure you've done enough research to know this is not right! Less is more (more recovery, more results, more free time!)