Many doctors now days order labs even tho they probably not needed. I've always had doctors who take the wait and see approach.
I sguest this is for many reasons. First, patients want tests. You could say is this necessary? What are you concerned about that tests would reveal. The patient can, and I believe should, be involved in decisions.
Another reason may be related to how often people sue. I suggest some tests are to make patients happy and to protect themselves from unhappy/angry patients and law suits.
Bottom line. Tests are not ordered.because it's likely something is wrong. They're ordered for a variety of reason's. Relax, your son's muscles are most likely sore because of gymnastics or growing pains. Achy muscles are common