I've seen a few cases in the military over the years - none involved Cross Fit incidentally, just stupid people and folks leading physical training with poor cognizance of what happens to the human body when you don't rest and hydrate properly...and tossing in over the counter anti inflammatory meds without really knowing what they do to the body.
Two off the top of my head ended up in ICU - one after a BFT they hadn't trained for and were in fact quite out of shape to begin with, the other at RMC during Indoc when some kids were run into the ground by their Squadron seniors a couple times a day during one of the worst Humidex weeks that summer and one hammered in bad.
MM