Melanie Oudin has played in the quarterfinals of a U.S. Open under the lights of tennis’ largest arena.

On a quiet Monday in late November, though, this professional athlete had something in common with the weekend warrior who makes a New Year’s resolution to get fit. Oudin hadn’t seriously lifted weights in two months, and all of a sudden she was pushing through an intense session.

She wound up in the hospital.

The 22-year-old American was diagnosed with rhabdomyolysis, the result of muscles breaking down and releasing proteins into the bloodstream, which in severe cases can cause kidney failure. It’s the same condition that sent 13 Iowa football players to the hospital in January 2011.

Athletes, both elite and recreational, are susceptible, but doctors aren’t exactly sure why some grueling workouts lead to the disorder while similar ones don’t.

“Other athletes need to trust your body and realize if you feel something that you’ve never felt before and it’s something new and worse, there might be something wrong,” Oudin said last month.

Dehydration is a risk factor for rhabdomyolysis, and doctors think that contributed to Oudin’s problems. It didn’t appear to be an issue for the Iowa players, but they had something else in common with Oudin and others with the diagnosis: an intense workout immediately after a long break.

Iowa took three weeks off after its bowl game, then returned with a session that included 100 back squats at half of the maximum weight each player could manage for one lift. The set had been done in 2004 and 2007 but with one major difference — the players weren’t coming off a rest period.

An investigative committee report commissioned by the school called the workout a test of physical stamina, mental toughness and who “wanted to be on the team.” Shaun Prater, then an Iowa defensive back, described the mentality that elevates athletes to lofty achievements but can also land them in the hospital.

He was going to be a senior, a player who had considered turning pro but stayed to try to win a championship. As miserable as he felt during those squats, he kept thinking: “I can’t throw up in front of these guys — I’ve got to be strong.”

“There were plenty of times when I wanted to say, ‘I’m not doing this,’” he recently said. “But I couldn’t. I’m a senior. I wanted to lead.”

He was in so much pain the next couple of days, he couldn’t bend down to take off his shoes. After four players told trainers about symptoms that included dark urine and muscle swelling, medical staff sent a text message to the entire team to see who else might be experiencing similar problems.

Prater was one who responded. He went to the hospital that night expecting to go through a few tests then head home.

He was there a week.

When his results came back with dangerously high levels of a protein called creatine kinase in his blood, Prater recalled, “The lady was freaking out. She was in tears. ... She was like, ‘Yeah, one more workout and you could’ve fallen into a coma.’”

He played for Iowa in the fall then was drafted in the fifth round in 2012 by the Cincinnati Bengals. Prater started three games for the Minnesota Vikings this season.

The investigative committee cleared trainers and coaches of any wrongdoing and made several general recommendations to prevent a recurrence, including scrapping the workout with the back squats. School officials said they had adopted those recommendations but declined to discuss what specific protocols have been changed.

Researchers at the university published a report on the cases in the September issue of the Clinical Journal of Sport Medicine. Among the findings: Players who were affected were significantly more likely than their teammates to report muscle failure and that they didn’t believe they could complete the workout.

In other words, their bodies were telling them something was wrong.

Dr. Corey Slovis, the chairman of Vanderbilt’s department of emergency medicine, put it this way: “Doing anything to true exhaustion is not smart.”

“I’m not against ‘no pain, no gain,’” he said. “But minor or moderate pain — it shouldn’t be severe pain.”

He believes athletes at all levels have become wiser in recent years about the importance of staying hydrated and taking breaks. The dangers of rhabdomyolysis have been raised recently in connection to CrossFit workouts, but Slovis said cross-training that includes multiple types of exercises is generally less of a risk factor than regimens that require repeating a particular motion over and over.

Oudin now knows to listen to her body. A day after the weightlifting session, she couldn’t straighten her arms. At one point, another player said, “Whoa, Melanie, you’re so jacked after one day of lifting.”

But her biceps weren’t bulging — they were swelling.

Oudin is expected to make a full recovery, but she was forced to withdraw from qualifying for the Australian Open.

Oudin reached the U.S. Open quarterfinals as a 17-year-old in 2009, and in her drive to try to return to that level, she learned that pushing herself to the limit can easily turn into pushing herself past the limit.

“If someone is (lifting) something a bit heavier than you, you want to push yourself to do what they’re doing,” she said. “There’s a fine line of knowing when too much is enough.”

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