What on earth is ‘rhabdo?’

For the past two weeks, almost every runner I know has been talking about one word: rhabdomyolysis.

The reason is heartbreaking. Rachel Apa, a 24-year-old former Division I field hockey player at Bucknell, collapsed two miles from the finish line of the New York City Marathon. She later died in the hospital. The initial diagnosis was rhabdo.

The running community is shaken. Group chats are full of warnings, and some runners are wondering whether to sign up for their next race at all. I understand the fear. But with all compassion for Rachel’s family, I do not believe her death is a reason for the rest of us to be alarmed.

I know rhabdo personally. In 2018, I ran my first marathon, the Dream Marathon, a program built for first-timers. I skipped the training sessions, even the sendoff. I had neither the discipline nor the patience. The longest I had ever run was 10K, mostly on a gym treadmill. Race-day adrenaline carried me through the first half in about 2:30. Then my legs turned to cement. I sat on a sidewalk in pain for half an hour, then limped to the finish. I left my hotel room in a wheelchair.

At the emergency room, blood tests showed mild rhabdomyolysis. I was confined for intravenous hydration and monitoring, and told to rest completely.

Rhabdo happens when skeletal muscle breaks down rapidly and releases its contents into the bloodstream, particularly a protein called myoglobin. Myoglobin can damage the kidneys and, in severe cases, cause acute kidney failure. Severe cases can also bring dangerous potassium elevation and cardiac arrhythmias.

That sounds terrifying, but look at what caused mine. I took a body accustomed to 10K and demanded 42K. That is the real danger of rhabdo: forcing your muscles to do something far beyond anything they have ever experienced. My muscles had not been prepared, and they broke down.

Runners who train properly are in a different position. My coach, Ken Mendola, builds plans that raise the distance gradually, up to a 32K long run before race day. Over weeks and months, muscles, tendons, and the cardiovascular system adapt to the load. A well-prepared long-distance runner is unlikely to develop serious rhabdo. The exceptions are a pre-existing condition or extreme environmental factors.

The environment matters a great deal. A study by Farrell documented a sharp rise in rhabdo cases at the 2022 New York City Marathon (which I ran), with 24 marathoners treated, compared with the three or four usually seen. Running generates enormous heat, and some marathoners’ core temperatures can exceed 104 degrees. In hot, humid conditions, sweat does not evaporate and cool the body. Heat also speeds up muscle breakdown, and dehydration compounds the problem. The spike came from conditions, not from the marathon itself.

I should also be honest about what we do not know. Marathon-related deaths are extremely rare, and severe rhabdomyolysis is also uncommon. We cannot responsibly say what share of marathon deaths it explains. I also will not speculate about Rachel’s medical history or what else may have contributed. That is for her doctors and her family.

So what should runners do?

Train progressively, and respect the build-up rather than running a distance your body has never seen. Respect the weather: on a hot, humid race day, slow down, hydrate, and adjust your goals. Know your own health, and talk to your doctor if you have a pre-existing condition. Learn the warning signs, too. Early symptoms include exhaustion, weakness, nausea, vomiting, and muscle aches. Severe pain or swelling, profound weakness, or dark, cola-colored urine after a race call for immediate medical attention.

I have been running marathons at least once a month, sometimes twice a month (on top of hybrid races). I believe I can do this safely because I treat most of them as long runs and do not push hard every time. I choose one “A” race, and that is the one where I follow a full race strategy.

Do not fear the marathon. Prepare for it, respect the conditions, and listen to your body.