Why is ‘strenuous’ exercise sending some young women to the hospital?

With music blaring, the lights dimmed and her feet stuck into the pedals of the exercise bike, Kyra Fancy’s adrenaline started pumping.

It was her first spin class – and also her last.

“(The instructor) was giving us more instruction about making the resistance harder on the bike and going faster and going up and down and you’re dancing on the bike,” recalls Fancy, who took the class in December 2023.

She said that midway through, her muscles started hurting, but not in the usual way.

“I felt like my thighs were getting really weak,” Fancy said. It felt as if the muscle in his right leg had “torn”.

Fancy said she felt pressure to move because she was unable to separate her feet from the pedals and did not feel like she could ask for help.

“I didn’t know anything bad could happen other than some muscle soreness,” said Fancy, who was 24 at the time and frequently went to the gym for cardio and strength training.

But a few days after the workout, she said the pain in her legs became “excruciating” and her urine turned dark brown.

“I felt like I was dying,” said Fancy, who lives in St. John’s.

At the hospital, she was admitted with a life-threatening condition called exercise-induced or exertional rhabdomyolysis, rhabdo for short.

Disease may occur after intense exercise And it occurs when muscle tissue breaks down, causing enzymes and proteins to leak into the bloodstream. These substances can cause an imbalance of electrolytes, which can lead to dehydration and cardiovascular problems. And excess amount of protein can harm the kidneys.

In March, Newfoundland and Labrador health services increased Concern over a rise in cases over the past few months among young women in some parts of the province.

Saint John is seeing a rise in cases

“We’ve seen a lot of activity due to this in terms of fairly vigorous exercise and people posting what they’re doing,” said Dr. Richard Barter, clinical chief of emergency medicine for Newfoundland and Labrador Health Services in St. John’s.

Between October 2025 and April, emergency rooms in the eastern region of the province, which includes St. John’s, recorded 20 cases of rhabdo. — Most of the women are between the ages of 19 and 30. It’s a “worrying” trend, Barter said, noting that the region would typically expect to see eight to 14 cases in any given year.

Exercise-induced rhabdo cases are not tracked across Canada, although Barter previously said the typical rate of rhabdo is about 4.5 to eight cases per 100,000 people each year. Research in the United States found that, between 2000 and 2019, the condition sent more than 40,000 Americans to hospital emergency rooms.

That study found that exercising without equipment, weight lifting, and soccer were the most common activities that provoke rhabdo. Most of the cases were in men aged 16 to 35. A 10-fold increase in ER visits was seen from the first decade to the second decade.

Although the study did not look at what was behind the increase, its researchers speculated that changes in exercise trends likely contributed, with high-intensity interval training (or HIIT) classes becoming more popular in 2014 and weight training in 2015.

What causes Rabdo?

According to Dr. Mark Tarnopolsky, division chief of neuromuscular and neurometabolic disorders at McMaster University in Hamilton, rhabdo usually occurs after “abnormal exercise.”

“This usually happens when you do something you’re not used to and you really push it too hard,” Tarnopolsky said. This can also happen when people return to work after taking some time off, he said.

Whenever you do a new exercise or start working out again after a break, it is common to feel stiffness or stiffness in your muscles in the days that follow.

“If it’s really extreme and you can barely bend your legs, your arms are stuck and you can’t straighten them and, or you start having dark urine… that means you’re damaging your muscles so badly that protein is coming out in the urine,” he said.

When that happens, Tarnopolsky said people should go to the emergency room so they can start giving IV fluids to keep things from getting worse.

In rare cases, when protein levels in the bloodstream become too high, they can damage the kidneys and the person may need dialysis, Tarnopolsky said. He said that although it is possible that it could result in long-term kidney damage, it is unlikely.

This condition can also cause compartment syndrome, in which the muscles become so swollen that they have to be cut to relieve pressure. Again, Tarnopolsky said, this is a rare result.

Other potential issues include Seizures, blood clots, or heart arrhythmias resulting from electrolyte imbalances.

Are trending workouts contributing?

Experts question whether social media is playing a role, with people challenging themselves or their friends to participate in strenuous activities, or whether fitness influencers are encouraging people to work out in ways they may have never done before.

“Avoid influencers on the Internet. That’s where you run into problems,” Tarnopolsky said.

But there hasn’t been much research done on this, so it’s hard to know for sure.

Heat also plays a role, Tarnopolsky said. High temperatures increase muscle breakdown And this can lead to dehydration, which affects the kidneys.

Since one of the biggest risks is overexerting yourself, Tarnopolsky said you can experience rhabdo no matter how fit you are. Research has found that it often affects both military personnel And athlete.

But that doesn’t mean people can do intense workouts, provided they follow a certain diet and exercise regimen, said Tarnopolsky, who works with a small number of people who actually have the genetic disorder that makes them more prone to getting rhabdo.

how to stop it

Melissa Denny, owner of Peak Performance Training and Nutrition in Brockville, Ontario, said she is on high alert for possible cases of rhabdo.

“There’s a lot of pressure on social media to get back to the supermodel look,” she said. “So people are really training super, super hard and holding really intense classes like spin, HIIT.”

But, Denny said, people forget that proper diet, hydration and recovery are a big part of the equation.

Denny said the top priority during his classes is keeping people safe. Her instructors do this by keeping class sizes small so instructors can check on everyone, provide water and a cool towel, and remind them to take breaks and hydrate.

In the meantime, Dr. Tarnopolsky said the main ways to prevent rhabdo are to stay hydrated, listen to your body, and go slow if you start a new form of exercise. He said that if you have already had rhabdo, you are not likely to get it again.

Even though she has fully recovered, Fancy still hasn’t gotten over what happened to her in spin class more than two years ago.

“I still struggle with panic attacks, sometimes when I try to go to the gym,” she said. He said he has created a home gym, which makes him feel more comfortable.

She also sticks to “gentle activities” that are helping her “build a healthy relationship with exercise.”