Still entrenched in the CrossFit culture of deplete, endure, repeat, she quieted the alarms and stoically pressed on to go to work. It didn’t take long to realize she not only couldn’t bend her arms, they also had no strength. She wasn’t able to treat her patients. By that evening, her slender arms had continued to swell into plump hotdogs of ache and regret, and she was starting to come to the realization that the morning’s danger alarms were legitimate.
Unbelievably, it took another 24 hours for her professional sense to break through the grip of the CrossFit culture, and seek medical attention. She was diagnosed with acute rhabdomyolysis, and ended up in the hospital for over a week. While in the emergency department they tested her creatinine kinase (CPK) levels. Normal is about 100. Her CPK levels were more than 45,000, a number that indicated damage to the kidneys.
While in the hospital, she called to cancel her CrossFit membership. As is standard when something is cancelled, the CrossFit coach asked the reason for her decision. She replied, “I’m in the hospital.” The instructor quickly asked, “Is it rhabdo?”
Rhadbo is short for Rhabdomyolysis and its description reads like something from a comic book (exploding muscle cells poisoning your kidneys, eventually killing you). It’s caused by consistent, extreme exertion.
The NYT ran an article on this in 2005:
Yet six months later Mr. Anderson, a former Army Ranger, was back in the gym, performing the very exercises that nearly killed him. “I see pushing my body to the point where the muscles destroy themselves as a huge benefit of CrossFit,” he said.
I think it’s safe to say that anyone that works out until their muscles explode isn’t playing with a full deck. These people are addicted to exercise. But isn’t working out a good thing? Well, for most people so is losing weight, yet we have anorexia.
One amusing consequence of these stories is that people might use it as an excuse for not working out at all. Or at least to make themselves feel better about not working out.
Not Unreasonable 
Like pretty much everything else in life, it is about moderation. I think Crossfit is dangerous for some people for some of the reasons you touched on, namely they think they are doing something good for themselves, and for the most part they are. Personal common sense has to prevail. I have seen an Army colleague in the hospital with Rhabdo from overexerting himself during an exercise, he was exhausted and was too proud to take a knee (The Army…talk about a dangerous culture). You are right that working out can be addictive, and the culture of Crossfit can exasperate this (a friend recently dropped a couple Gs on his home gym). However, a reasonable person with a good coach will reap great benefits.
It cuts to the heart of what an exercise regime is. In reality exercise benefits can be realized doing just about anything. The point of a routine is motivation and that is what Crossfit (or Billy Blanks or Richard Simmons or anything) offers.
To do so the culture needs to celebrates overcoming barriers that the vast majority of people face. Thinking of cultural benefits as an optimization problem (what cultural institution best provides motivation for achievement?) in some ways it’s comforting to know what the limit case is. As my grandmother always said about bridge: if you don’t go down once in a while you’re not betting your hand.
But, again, these people who work out till they die are clearly out of their minds and any extreme-achievement culture without fail-safe breakers to identify such wackos should be castigated.