Unless you're at a very advanced level or chemically assisted, you don't need to go a full week in between training a specific muscle group.
Because muscles need approximately 48 hours rest to replenish themselves. This i know. To avoid boring myself I switch up my workouts every 6-8 weeks. I'll do a cycle where I do push, pull, push, pull, legs. Then I'll do one where I do circuits. Then I'll do legs and back, chest/tris/shoulders and go back and forth between those. The time I saw my best gains was when I did one muscle group a day actually.