I would agree that 4 days is indeed very short notice for the MR or any substantial high altitude hike. I've done many marathons and never heard that the "rip" in muscles will come about through running, at least not significant tears and then rebuilding. I thought this was more through weigh lifting, that's why you're not suposed to work certain muscles groups on consecutive days when lifting: biceps, triceps, deltoids, etc.
But hey-- if you think you're ready, more power to you! I would lay off any big hikes the day preceding the MR. Just rest up and do a little dinky hike, like to Lone Pine Lake or something.