I can only speak to my experience. When my daughter was out and forced to rehab, cross train, she came back stronger and in better condition than she was before she went out. Her Dr's, Surgeons, and Physical Therapist are shocked that we do not have an off season and we do not cross train. Cross Training does not allow for "muscle deteration", it strengthens the mussels that do not get worked from single use movement. Making for balanced strength. Now if you sit on the couch during this break eating ring dings and drinking sweet tea that is a different story.
In fact her orthopedic that worked her Stress Fracture, is also a Dr for the Philadelphia Eagles and uses words like, negligent, and insane when he speaks to the issue of the amount of repetitive motions on a youth body, mussel fatigue and limited recovery after work out, and the lack of down time and off season in cheerleading. Did he treat the injury aggressively as an athlete, yes, but he also put her in a hard cast when he could have gone with the boot, knowing that there would be a chance she would take the boot off to cheer. He also had her in aggressive rehab that addressed the issues on both feet. He refused to allow her to wear a brace once she was cleared to return, as he wanted her to build her mussels up.