In this article we share the lessons we’ve since learned about “exertional rhabdo.” While high-intensity exercise is essential in obtaining and maintaining optimal health and fitness, it’s important to be aware of when too much is too much.

“Countless bad-asses from sporting and special operations communities, long regarded as bulletproof, have been burned at the stake of ego and intensity.”

As it turns out, the burning is rhabdo, and we now find ourselves obligated not just to explain CrossFit’s potency but to warn of its potential lethality.

We can dispense with much medical detail with a quick and easy description of rhabdomyolysis as a potentially lethal systemic meltdown initiated by the kidneys in response to the presence of shed muscle-fiber debris and exhaust in the bloodstream. There are several causes and types of rhabdo, classified by the underlying cause of muscle breakdown. With high-intensity exercise we are dealing with what is known as exertional rhabdomyolysis. It can disable, maim and even kill.