Cramming in high-intensity workouts to prepare for summer can, in rare cases, lead to a life-threatening condition

• Cramming intense exercise to shed pandemic pounds can, at the worst, lead to rhabdomyolysis.
• The rare, life-threatening condition comes when muscle tissue breaks down, overwhelming the kidneys.
• It mostly occurs after intense full-body exercises if you're new to fitness or don't ease back in.

When the coronavirus pandemic shut down the gym Jamie Hickey owns, his regimented diet and fitness routine was replaced by booze, cheesesteaks, and plenty of sitting.

By summer, the 42-year-old in Philadelphia was up 22 pounds, and it didn't feel good. Years ago he weighed 305 pounds, before losing more than 100 and launching his current career. He didn't want to relapse.

So when his brother, who had also put on pandemic pounds, suggested they compete to see who could shed the most weight in three months, "it wasn't hard to find the motivation," Hickey told Insider.

A few weeks into the competition, Hickey upped the weight on the squat rack after riding an exercise bike longer than usual. He said he felt a twinge in his leg that he ignored until he couldn't even sit to go to the bathroom.

Icing and pain relievers didn't help, and he woke up the next day with brown urine. "It was scary," Hickey said.

In the emergency room, Hickey was diagnosed with rhabdomyolysis, a rare condition caused when muscle tissue breaks down rapidly and releases a protein called myoglobin into the bloodstream. When the kidneys can't filter it fast enough, it turns a person's urine Coke-colored and can lead to organ failure and death.

With the promise of a blissful summer thanks to COVID-19 vaccines, people are rushing to transform their lockdown love handles into beach bodies. But cramming in intense workouts can backfire, leading to, in the most severe cases, rhabdo.

Hickey, who stayed in the hospital on IVs for three days and didn't fully recover for months, said his diagnosis was a wake-up call.

"I like to tell clients, especially men, to leave their ego at the door," he said. "My ego was: I'm going to beat my brother." His sibling still jokes that Hickey owes him a prize.

Rhabdomyolysis is rare but may be on the rise during and after the pandemic

There are so few documented cases of exercise-induced rhabdo that it's tough to know how common it is, but Dr. David Geier, an orthopedic surgeon and sports-medicine specialist, told Insider he believed it was underreported, with some people getting the condition mildly, not realizing what the pain is, and simply taking a few days off until they feel better.

Among the media and case reports that do exist, the condition has been described in people after football practices, CrossFit workouts, boot camps, SoulCycle sessions, half-marathons, and hiking the Grand Canyon.

More people may have gotten it during the pandemic, as people launched into tough workouts without guidance, Dr. Jose Torradas, an emergency-medicine physician outside Philadelphia, told Insider. While it's still rare enough for any one provider not to notice more cases, "the aggregate suggests an increase," he said.

One Reddit user and Peloton enthusiast wrote in February, for instance, that he suffered from the condition three times on his path to losing 40 pounds during the pandemic. "Don't overdo the frequency or intensity of your Peloton rides," he wrote. "The threat of rhabdo is real, and rhabdo really sucks."

In August, the dancer Ashley Elizabeth Daigle wrote in Dance Magazine that after recovering from COVID-19, a 15-minute ab workout led to rhabdo, which nearly destroyed her career.

"Since being quarantined," she wrote, "most of us have not been at our usual activity levels, and we are underestimating how much our routines have changed."

The countdown to summer - plus the season's increased risk because of heat and dehydration - could prompt an uptick, too. "Some people are picking up the gym really late and want to lose 50 pounds by June," Irving "Zeus" Hyppolite, a personal trainer and the founder of House of Zeus in New York, told Insider's Gabby Landsverk earlier this month.

Rhabdo is usually caused by intense full-body exercises that your body isn't used to

Accidents, like a serious car crash that crushes the muscles, can also cause rhabdo, but among exercisers, it's most likely to strike from intense full-body exercises in which more muscle proteins are liberated.

For instance, CrossFit and weight rooms can be culprits, while it's not as common among cyclists.

"Rhabdo happens when you basically break down so much muscle protein that it overwhelms your kidneys, and it's more likely to do that with a full-body workout than just lower body," Dr. Jordan Metzl, a sports-medicine physician, told Insider.

And it's not just fitness newbies who are at risk. Folks who are in good shape but have taken a break and push themselves too fast can also suffer. In 2011, for example, ESPN reported 13 players on the University of Iowa football team were hospitalized with rhabdo after their first training session after winter break.

"It's typically people either that haven't been exercising much at all and then go zero to 60, or people that are in fairly good shape but have taken a break for a long period of time, and then they get back into it too fast," Metzl said.

Some people have a higher risk of rhabdo

We all have a different physiological limit, and some people are more predisposed to rhabdo than others, Metzl said.

Take Samuel Levshteyn, for example, an 18-year-old who has experienced the condition twice in the past three years.

The first time was after a three-hour tennis match one May. Levshteyn said he collapsed on the court after jumping for an overhead shot. After wobbling off the court with the help of trainers, he was able to ease the pain by drinking Gatorade and water, eating bananas, and massaging the cramps, he added.

But after 30 minutes lying on the couch, the cramps returned and he was unable to sit up. "I couldn't think about anything in the slightest. The pain in my legs was the worst pain that I had been through in my entire life," he told Insider.

He got an ambulance to hospital where he stayed for two nights on an IV. He said he was told that if he had stayed at home, he would have likely experienced kidney failure.

About a year later, Levshteyn got rhabdo again after a long match on a hot day - this time, it was less painful, but he still went to hospital for a few hours, he said.

Levshteyn has learned how critical it is to hydrate. "I haven't been as active now due to the quarantine," he said. "But I definitely drink a lot more water and eat more snacks throughout the day, especially if I know I plan to do some physical activity."

Don't be afraid of working out hard, but listen to your body

To minimize your rhabdo, listen to your body and don't push yourself to exhaustion. Be aware that it's more likely in hot, humid conditions.

Know the symptoms, too: While a good workout will often result in delayed-onset muscle soreness, rhabdo's telltale signs are muscle pain, weakness, and myoglobinuria, or dark urine.

When in doubt, seek medical help right away and drink a lot of fluids - doctors will likely put you on an IV and rehydrate you aggressively.

While some people develop rhabdo, Metzl said, most people do not, and we shouldn't use it as an excuse not to work out hard.

"You can work very, very hard, and most people won't get rhabdo," he said. The key takeaway is to build things up gradually.

That will prevent not only rhabdo but also more common overuse injuries Hickey is now seeing in his gym. "These people are in very good shape and are lifetime fitness enthusiasts," he said. "I don't even need to teach them anything. They just need to realize that they have taken a step back and need to be patient."