Is training each muscle group once a week sufficient for maintaining muscle?

Say, I don't want to get any bigger but I want to keep the miscle I have earnt. Is eating enough protein and training each muscle group once a week with high intensity enough to maintain the muscle?
I'm talking about a split like this;
Monday; Legs and glutes
Tuesday: Rest
Wednesday: Abs
Thursday: Rest
Friday: Upper Body
Saturday: Maybe a light leg work out.
Is training each muscle group once a week sufficient for maintaining muscle?
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