before 2 weeks ago i've been training each muscle group twice a week w/ 2 days rest in between. i've gotten stronger from this and gained size in the past 4 years, but i just switched over to working out 1 muscle group per week and i can already feel the difference. it also gives me more time to train each group with more exercises. i'm gonna try out my new routine and see where it gets me within the next year
Good luck! i've made my best gains training each muscle once a week.