Bodypart once every 5 days if trained heavily.
What's so difficult about that ?
Overtrain, like in 20+ sets: once a week, cause of recuperation. But you'll grow slower.
Undertrain, like thrice a week. But you'll grow slower too.
So: you can still grow with once every 2 days or once a week.

I now it by now, go for once in 4-5 days.
Says The Doctor.