Hey /fit/ I know that you're supposed to switch up your lifting routine periodicly but just how often should you switch it up? Right now I have 2 routines that I switch on and off each month. One focuses on barbells for core excersises

>All flat, incline, decline bench press with barbell
The other dumbells

>All flat, incline, decline bench press with dumbells
This goes for each muscle, group
>One month barbell squat, barbell shoulder press. The next use dumbells for shoulder press, sumo squats

Is this a good thing to do? How do you guys switch up your routines