From the WebMD Archives

Feb. 22, 2018 -- Nancy Weindruch wouldn’t have called herself an athlete in 2015, but she was a regular gym-goer who loved to ski, golf, and do yoga. She was excited to try something new when her sister invited her to a cycling class for the first time. Within 15 minutes of getting on the bike, she knew she was in way over her head.

The lights were dim. The music was blaring. Everyone was in sync with the high-energy, intense exercise -- except her. “The instructor was encouraging everyone to give it your all, and I was looking around the room and thinking, 'I can’t do this.' I realized very quickly my body didn’t have the endurance for this,” Weindruch recalls.

She was on the opposite side of the room from the door, too embarrassed to get up and leave and unsure she could unlock her shoes from the bike without causing a disruption. So the then-30-year-old sat down on the bike, turned its resistance to the lowest level, and slowly pedaled through the rest of the class.

“When I got off the bike I felt weak in my legs, but I didn’t really think anything of it,” Weindruch recalls. “I just figured it was a new class for me and it will pass.”

Three days later, she could hardly walk and was struggling to sit in a chair. “My intuition kicked in, and I thought something isn’t right,” she says.

A quick Google search turned up a story about a 30-year-old woman who had similar muscle pain after a cycling class and was hospitalized with something called rhabdomyolysis, or rhabdo for short. Weindruch didn’t have all the symptoms described in the story, but she had enough that she went straight to the emergency room.

Once there, lab results confirmed she too had rhabdo. She was admitted to the hospital for a week. “The pain was so excruciating that it contributed to nausea,” Weindruch recalls. “It was unbearable. The worst pain I’ve ever experienced.”

The disorder is dangerous but rare. In one study, 22 people out of 100,000 were known to have it.

What Is Rhabdo?

Rhabdomyolysis is a syndrome involving muscle breakdown and damage. When muscles are injured, they release their contents, including a muscle enzyme, into the bloodstream. The enzyme can harm the kidneys and can cause kidney failure in up to 40% of cases. It also can harm the kidneys’ ability to remove urine and other waste.

Rhabdo can be even more dangerous in children when they're pushed to extremes in sports or other physical activities.

Patients generally recover when they get prompt treatment, but the condition can lead to death in rare cases.

The syndrome has three classic symptoms, but not all are always present. They are:

  • Muscle swelling
  • Muscle weakness
  • Dark urine (from the muscle pigment staining the urine) or less urination

Many things can cause rhabdo, including trauma, drug use, statins, severe dehydration, and extreme temperatures. But the growth in exercise-induced rhabdo is getting more attention.

“It can happen with any intense exercise if it involves repetitive motion of a muscle and new movement,” says Maureen Brogan, MD, an associate professor of medicine at New York Medical College in Valhalla, NY.

Brogan wrote an article on the subject in The American Journal of Medicine in 2016, saying rhabdo brought on by cycling class was a “public health concern.” She says she came to see it as that after six patients came to her hospital’s ER, and all involved people trying a cycling class for the first time. Each of them had received a free class pass. When she searched medical literature, 42 of the 46 cases she found also involved people going to cycling class for the first time.

“Those are the patients that were most at risk because they may not be conditioned and are using and engaging new muscle groups for the first time at an intense rate,” she says. “So even if you were a different type of athlete like a runner, and then you switch to biking and use quadriceps and gluteus maximus muscles at an intense rate -- that first time, you may be at risk of getting rhabdo.”

Brogan says people who stop cycling for some time and then go back at the same rate are at risk, too.

“(Cycling) is great exercise if you are conditioned for it,” she says. “But you burn 600 to 900 calories in one class. You wouldn’t go out and run 6 to 9 miles on your first day of running. If you did that, you wouldn’t be able to walk either.”

What We Know About Rhabdo

In her article, Brogan says things that raise your chance of having rhabdo are exercise intensity, a person’s conditioning, hydration, and body temperature.

Researchers say it’s tough to know how many people are affected by rhabdo, but in theory, any type of muscle injury can cause it. Several studies cite incidents connected to cycling class. A review of patients between 2010 and 2014 at one New York City hospital uncovered 29 rhabdo cases, 14 connected to cycling. Study author, Todd S. Cutler, MD, an assistant professor of medicine at Weill Cornell Medicine in New York City, says all 14 patients had similar stories.

“These were people who had either never done this before, or it had been a long time since they had done this, and they would usually make comments like, ‘I’m in pretty good shape’ or ‘I’m surprised this happened to me because I exercise.’ The point being that these were fit people,” Cutler says.

Military training is also connected to rhabdo cases. A 2012 study found it happening 7 to 8 times a year out of 10,000 military members. A 2010 study of military personnel in basic training found about 22 cases of it per 100,000 recruits each year.

Professional athletes have reported getting the condition too. Professional snowboarder Amy Purdy took to Instagram in 2016 to tell fans she was hospitalized with the condition, which she called “crazy” and “scary.” She says she got it after going to a CrossFit gym for the first time and doing intense pullups after not doing them for a few months. 

"It wasn’t until 72 hours later, I was back in my hometown with friends at a restaurant around 11 at night. I told them I worked out too hard a few days ago, and my arms wouldn’t straighten all the way. I then took my jacket off and instantly noticed swelling around my elbows on both arms," she recalls. 

She remembered something similar happening to a friend and rushed to the hospital. 

"The doctors were convinced I didn’t have it because my arms were only slightly swollen. They decided to test me anyway,” Purdy says. "That whole experience was one of that hardest experiences of my life!" 

She says it's important for people to know that rhabdo can happen to anyone, no matter how often you work out or how in shape you are. 

"If you push your body to failure and keep going, you are at risk. Listen to your body. It knows best," Purdy says. "And if you find yourself going on days with overly stiff and sore muscles and you notice swelling, get to the hospital ASAP. It may not be rhabdo, but a simple blood test can tell.”

Alexis Colvin, MD, an orthopedic surgeon at Mount Sinai Hospital in New York City and the chief medical officer for the U.S. Open Tennis Championships, says she’s also heard of cases connected to marathons and ultramarathons. “There is definitely more awareness of it with the popularity of people looking for different ways of challenging themselves,” she says.

In her article, Brogan describes three first-time cycling class-related cases that she felt reflected patients not seen widely in the medical literature -- either because of their young age or the severity and quick onset of their symptoms:

  • A 20-year-old man who regularly exercised
  • A 33-year-old woman who got rhabdo after just 15 minutes on a cycling bike
  • A 33-year-old woman whose case was so extreme, she needed hemodialysis

All these patients needed physical therapy.

“These three cases are all shocking. That is why I had to write about them. I want the public to know that you are at risk for going into kidney failure if you get rhabdo, and it is important to know how to prevent this from happening. Start (cycling) slowly,” Brogan says.

What to Do About Rhabdo

Experts say rhabdo shouldn’t scare people away from exercise or have them thinking they are in danger if they hit the gym. The syndrome is rare and happens in small numbers. But doctors say you should be cautious about rigorous exercise when you are just starting out.

“If you are going to engage in a high-intensity exercise regimen for the first time, you should start out at a level you can handle. If working with a trainer or exercise coach, they should have you do levels of increasing intensity over time, and not hit people so hard the first time out that they end up overworking their muscles to a degree they aren’t trained for. Those are the people who end up in trouble,” Cutler says.

It’s not uncommon to feel muscle soreness after working out, so how do you know if you’re dealing with rhabdo? Colvin says the pain seems extreme or out of proportion with the workout, and you would have it within a few days of the intense exercise.

“It’s about the trend in how you are feeling. In most typical recoveries, people tend to start to move in the right direction, but with rhabdo, that isn’t the case. Untreated, it will most likely get worse,” she says.

Brogan says be careful if you accept a free pass for an intense exercise class or try one for the first time. Her other recommendations include:

  • Stay well-hydrated before, during, and after the exercise.
  • Don’t allow your body to get too hot, since being overheated can help bring on rhabdo.
  • Don't take your first class in a heated exercise room.
  • Tell the instructor you are new, and ask for advice when just starting out.
  • Take breaks, and work at a slower speed.
  • Avoid non-steroidal anti-inflammatory drugs like ibuprofen, since they can also help bring on kidney injury.
  • After trying an intense exercise for the first time, wait a few days before working out again, because symptoms can take a few days to appear or worsen.

If you’ve recovered from rhabdo, Brogan says, there are no guidelines about how to go back to exercise. Many patients she speaks with have a fear of exercise after they recover. “I still speak to one patient who says her legs still just don’t feel the same,” Brogan says.

Purdy says it took her a long time to heal. "Take it slow. I spent months in rehab before I could lift even the lightest of weights again. It’s not something to take lightly," she says.

In Weindruch’s case, she was in the hospital for a week, getting pain medication and IV fluids. Doctors monitored her kidneys and vital signs, and it took several days for her pain to pass and her dark brown urine to return to its normal color.

Three years later, the now 33-year-old is still prone to dehydration but has returned to exercising. She sticks to low-impact options like the elliptical, walking, or yoga.

“It’s not that I’m traumatized. I just think it is a matter of listening to your body,” Weindruch says. “In our society, you see a lot of really intense physical activity, which is awesome, but I don’t think our bodies are meant to go from 0 to 60 unless you have done the proper training -- at least not mine.”

Show Sources

Maureen Brogan, MD, New York Medical College, Valhalla, NY.

Alexis Colvin, MD, Mount Sinai Hospital, New York City.

Todd S. Cutler, MD, Weill Cornell Medicine, New York City.

Nancy Weindruch, Washington, D.C.

Instagram: @amypurdygurl, Oct. 27, 2016.

Tennis World USA: “Tennis - Melanie Oudin diagnosed with rhabdomyolysis.”

U.S. National Library of Medicine: “Rhabdomyolysis.”

The American Journal of Medicine: “Freebie Rhabdomyolysis: A Public Health Concern. Spin Class-Induced Rhabdomyolysis.”

The Ochsner Journal: “Rhabdomyolysis: Pathogenesis, Diagnosis, and Treatment.”

Muscle & Nerve: “Natural history of exertional rhabdomyolysis: a population-based analysis.”

Rhode Island Medical Journal: “Exercise-Induced Rhabdomyolysis.”

Medicine & Science in Sports & Exercise, “Rhabdomyolysis in the US Active Duty Army, 2004-2006.”

Sports Health: “Spinning-induced Rhabdomyolysis and the Risk of Compartment Syndrome and Acute Kidney Injury: Two Cases and a Review of the Literature.”

Clinical Journal of Sports Medicine: “Increasing Incidence and Unique Clinical Characteristics of Spinning-Induced Rhabdomyolysis.”

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