Honestly just enjoy the time you have off do something you want to do, take some trips and detox from all school things. Otherwise the burnout will be real. If you do want to study something to feel "prepared" I suggest studying the location of every muscle in terms of the surrounding muscles and boney structures. Use a 3D anatomy app like essential anatomy, if you can learn to recognize things like "this is the where the middle trap is and under it is the rhomboids, and under the mid trap on the scapula above the scapular spine is the supraspinatus". Might seem simple but this will set you up to really dominate cadaver lab and practicals. Learning origin, insertion, actions and innervation as well as blood supply may be taught with different specificity depending on your professors and program which is one of the reasons I would pass over it for now.