Hi Cecilia,
It's always good to switch you off days to keep your body guessing but also depends on how tough the workouts you've been doing have been. You don't want to over max your body, as then you'll over train, and have to take some time off and start up again once your body recovers. My off days always depend on how I'm feeling, or what my routine is like, and sometimes a bit of both. If I'm already dragging by Wednesday and I know I got two really intense workouts to do Thursday and Saturday. I'll take Wednesday off or Thursday depending on when I feel super tired. Rest that day and come back fully charged. The one thing I noticed doing it this way. Is my harder workouts actually are easier with the rest/recharge day before them. I can really push myself more then if I had just struggled threw them, which then give me a bit more benefits. So to me it’s well worth the price of moving my rest day, even if it was an unplaned move. But in general I always try to take take a good look at my workout schedule for that week and plan when I'm going to have my rest day. I also always try to have no more then six workouts in a row without a rest day. With that rule my rest days really can hop around from week to week and my body never knows what's up.
HTH,
Kit
