Workout Splits

Full body training hits every major muscle group each session. It is the most efficient structure for two or three days a week, and the one most beginners should start with.

Upper lower splits the week into two upper body and two lower body sessions. For anyone training four days a week, it is hard to beat.

Push pull legs groups muscles by movement pattern. Run six days a week it delivers high frequency and high volume, provided you can actually recover from it.

Two meta-analyses reached different answers, and the second one explains the first. Frequency matters, but not for the reason it is usually sold.

It is not wrong, which is not the same as being a good default. The evidence says why, and the reason it fails is usually the calendar rather than the physiology.