I HAD seen the Uncle Rhabdo T-shirts before, on the muscled torsos of die-hard CrossFit fans. Uncle Rhabdo was a cartoon character, a sketchy-looking clown that made an insider’s joke out of rhabdomyolysis. That joke was hard to understand unless you lived in the world of extreme athletes. Uncle Rhabdo represented the absolute limit. Meeting him was proof that you had pushed your body to the very edge of its endurance—and beyond.

As a woman who had written about health and fitness since falling in love with weights a couple of years earlier, I had a pretty good fix on the mechanics of rhabdomyolysis. When muscle fibers break down too quickly, they release myoglobins into the blood. The body can’t process all these byproducts quickly enough, so these free-floating proteins can result in kidney failure or worse—much worse. You might expect to see rhabdo in a patient whose muscles have been traumatically crushed, say in an earthquake or a car crash. We extreme athletes, it turns out, have the ability to do the same thing to ourselves at the gym.

I looked at my swollen arm, as my husband shut the hospital room door, and I asked him not to turn the room lights on yet. With the door shut, the machines keeping me alive seemed comfortingly unreal. A silent mantra was looping in my head: “I refuse to die from doing too many pull-ups.”

The funny thing was, the workout that sent me here had been powered only by good feelings. I had scored a writing gig that would take me to Zambia in four days, followed by a once-in-a-lifetime vacation at Victoria Falls. My days as a professional power lifter were behind me, but a competitive spirit never really retires. So my trainer and I decided to go all out.

When my arm later became puffy and immobile, I beat a well-worn trail to the office of my sports physician, Dr. McKee. After a few tests, he came back with a crisp prognosis: rhabdo. “Liver damage. Danger of seizing, acute renal kidney failure, heart attack.” He also noted that the muscle tissue was in danger of becoming necrotic (that meant “dying,” a helpful, writerly part of my mind told me). My only hope? To flush my system with fluids and wait.

Lying there, I knew I faced a rocky night. My levels of creatine kinase needed to come down quickly to avoid the worst outcomes. And while they’re flushing you like a drainpipe, I told myself, maybe you can also figure out why you’re really here. That was the elephant in the room.

It’s a strange bargain to drive the body that hard. On the upside, some days you get to feel like a superhero, in tune with this beautiful bundle of muscle and bone that you travel the world with. The downside is that you’re always wrestling with that body’s limits. Weight lifting had brought me so much pride, but also a herniated disc, assorted minor injuries, and now this. “When you get better,” said Dr. McKee as I lay despondent under the covers, “you need to ask why you’re doing this to yourself.”

As fluids slowly cleared the damage, I left the danger zone. I stopped beating myself up when I saw my life was no longer in danger. Then Dr. McKee delivered another bombshell: Under no circumstances would I be getting on that plane to Africa. While I’d survive this encounter with Uncle Rhabdo, he’d take away something I’d set my heart on for months.

What is my body’s real peak condition? I asked myself that question as I rode home after my stay, weak as a kitten. I would get better. I would respect my body’s limits. I would be gentler with my fellow traveler.

But somehow within six months, I was back in Dr. McKee’s office. I had pushed too hard again. “The definition of insanity is doing the same thing over and over, and expecting different results,” Dr. McKee said.

I’m still trying. It’s been almost two careful years now. I’m trying like heck. I need to find the balance between the discovery of what this body can do, and some peace with its tender limits.