Just two days after the start of the winter strength-and-conditioning program, Jim Poggi, a University of Iowa freshman football player, called his father to report that his body ached from the intense workouts. The pain in his arms and legs had not subsided even after a weekend of rest.
"He called afterwards and said it was hard work and he was very, very sore," Biff Poggi said of his son.
By the third day of workouts, on Jan. 24, it was clear something had gone terribly wrong. By the next morning, Poggi and 12 of his Iowa teammates were hospitalized with rhabdomyolysis, a condition in which muscle tissue breaks down and floods the bloodstream with a protein that can impair kidney function.
This type of rhabdomyolysis, caused by physical overexertion, was once rare. But the condition is cropping up with increasing frequency in the world of amateur athletics, experts say, perhaps the result of a culture in sports that emphasizes superior conditioning and physical tenacity.
"There is more risk of it now because the use of strength coaches is becoming more widespread," said Dr. Lyle Micheli, director of sports medicine at Children's Hospital Boston. "At the high school level, strength training was unheard of 10 years ago. Now strength training is de rigueur."
The last of the 13 Iowa football players was released from the hospital last weekend, and all are expected to fully recover. But the incident echoed several other outbreaks of rhabdomyolysis on amateur teams around the country in recent years and has raised questions about the vigorous training methods employed in some sports settings.
In 2007, seven men and women on the University of South Carolina swim team fell ill after resuming workouts following a summer break. A 2005 report in the British Journal of Sports Medicine described 119 cases that developed among Taiwanese high school students who were instructed to perform 120 push-ups in five minutes. And last fall, 12 members of the McMinnville, Ore., football team — which won one game in 2009 — were hospitalized for rhabdomyolysis after beginning an "immersion" training camp to prepare for the new season.
"Rhabdomyolysis is more common than is realized," said Dr. E. Randy Eichner of the University of Oklahoma, who has studied the condition. "It's too much exercise, too fast, too soon."
Rhabdomyolysis has numerous causes, including viral infection and severe burns. Certain medications, such as cholesterol-lowering statins, can trigger the problem, as can cocaine and possibly some nutritional supplements such as creatine.
In the past, exertional rhabdomyolysis was mostly seen in isolated cases among military recruits or marathon runners. Some deaths have occurred, and police and military trainers are now well aware of the problem, said Priscilla M. Clarkson, a University of Massachusetts kinesiologist.
But in the civilian world, coaches and trainers often know little about the illness, said Steven A. Hawkins, chairman of exercise science at California Lutheran University in Thousand Oaks.
It's difficult to know when vigorous strength training has crossed the line and athletes are at risk of rhabdomyolysis, Clarkson said. Tiny tears occur in muscles after any strenuous workout. The healing of these micro-tears, which causes the soreness people feel after hard exercise, is what prompts the muscle to become stronger.
But the tears release a protein called myoglobin into the bloodstream. If too much myoglobin is released, it can build up in the kidneys and impair function. Treatment includes intravenous fluids and sometimes kidney dialysis.
Dehydration increases the risk. Eccentric exercise, in which muscle fibers are lengthened as they contract — such as with squats and push-ups — is usually involved in triggering the syndrome, Clarkson said.
However, some cases of rhabdomyolysis also appear to involve a coach's or trainer's enthusiasm for working athletes to the brink of collapse, Hawkins said.
It's still unclear why so many Iowa football players fell ill. The school and the Iowa Board of Regents have ordered an investigation of the incident.
The players reported for their first day of winter workouts on Jan. 20, following a break since the team's Dec. 28 victory over the University of Missouri in the Insight Bowl. The students undertook a grueling, lower-body workout including 100 squats done in rapid succession, according to Biff Poggi. The next day, a strenuous workout focused on the upper body.
Four days after the workouts began, one player contacted a team doctor complaining of symptoms resembling rhabdomyolysis, which include extreme muscle pain, swelling in the limbs and dark, tea-colored urine. The dark color comes from the myoglobin in the urine.
After a second player showed up with similar symptoms, the physician notified the training staff, said Tom Moore, University of Iowa spokesman. Eventually, 11 more athletes were diagnosed and hospitalized with cases that varied in severity.
"I suspect if there wasn't that one or two people who got a severe case, those others wouldn't have gotten to the hospital," Clarkson said. "They would have toughed it out. And we wouldn't have heard about it."