Left untreated, the muscle injury syndrome known as rhabdomyolysis can be life-threatening.
It’s relatively rare: a 2012 study found 382 to 419 cases per year in the U.S. army between the years of 2003 and 2006.
According to the Cleveland Clinic, roughly 26,000 people develop the syndrome each year in the U.S. There is no data available for the number of cases in Canada.
However, when it does occur, it’s intensely painful and dangerous.
“It basically causes our muscles to break down and leak some of the muscle cell contents into the bloodstream,” Dr. Jane Thornton, a clinician scientist and sport medicine physician, told Global News.
One protein, called myoglobin, is of particular concern.
“That (protein) carries oxygen within your muscle, and that’s cleared by your kidney,” said Cameron Mitchell, assistant professor of kinesiology at the University of British Columbia.
“The issue we see is a build up of myoglobin, which can cause damage or problems with your kidney. That’s when it becomes a clinical issue.”
Both Mitchell and Thornton don’t want a fear of rhabdomyolysis to scare people off from exercising, because it’s very rare and exercise is still highly recommended to stay healthy.
“As someone who has been a high performance athlete for a long time, I try to really promote physical activity for my patients,” Thornton, a rower who competed at the 2008 Summer Olympics, said.
“I want to emphasize that exercise is generally safe. We don’t want to deter people from doing that.”
However, rhabdomyolysis may be a reason to slow down and ensure you’re doing things properly.
Most people experience a small degree of muscle damage at some point, Mitchell said, and it’s typically caused by intense, repetitive exercise.
“We see something that happens really commonly, called delayed-onset muscle soreness (DOMS),” Mitchell said. “It’s basically muscle soreness that peaks 24 to 48 hours after exercise, and other than being uncomfortable, it’s not a problem at all.”
In fact, Mitchell said, some athletes seek DOMS because it makes them feel like they had a successful workout.
However, rhabdomyolysis is something completely different.
Signs and symptoms
It’s described as severe muscle pain and weakness caused by muscle breakdown and muscle death, according to the Cleveland Clinic.
“This dangerous muscle damage can result from overexertion, trauma, toxic substances or disease,” says the website.
However, the key difference between rhabdomyolysis and other muscle pain, like DOMS, is a change in urine colour.
“Brown or tea-coloured urine is the main marker,” Mitchell said.
According to Thornton, symptoms can begin mild.
“You can have pretty mild symptoms at the beginning, where you just kind of feel sore and achy like a lot of us do after exercise,” she said. “The difference is that … after a day or two, it usually tends to get worse instead of better.”
Thornton has also seen the syndrome cause nausea, vomiting and abdominal pain.
If you experience the symptoms of rhabdomyolysis, it’s important to seek treatment to avoid any long-term damage.
Treatment includes I.V. fluids to hydrate the body and help support the kidneys, which can get damaged as a result of the increase in waste being filtered through the organ.
“We have to support the kidneys … and the way to do that is hydrate and replace any kind of electrolytes that were lost,” Thornton said.
The extreme consequence of rhabdomyolysis is kidney failure — which would require a treatment called hemodialysis — but that’s very rare.
“Most people are healthy enough that they’ll recover,” Thornton said.