think of the shock your back will get once you switch from one to the other, shock, adaptation and growth, plateau, repeat
When I was a soldier in Germany in the 80's I went out drinking one night and couldn't remember where I parked my car the next day. had to bike 18 k each way to the base every day for 10 days, my legs got shocked and grew a ton quickly to compensate for the new exercise. Eventually the polizi came and got me to pick up my car, it was down this hill parked on a sidewalk lol Point is if you shock the hell out of your muscles, they'll adapt cause they have to. if you do lose anything during a month's rest it won't be much and will be more than made up for during the growth cycle