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A running laboratory: Marathon to test more than speed

Lara Kucera

The Silicon Valley Marathon offers researchers the chance to study such events’ effects on heart muscle.

BY EWEN CALLAWAY

More than 1,000 people will run the Silicon Valley Marathon between San Jose and Los Gatos on Oct. 29. Sixty of those participants will get much more information than their times when they cross the finish line. Immediately after the race, a pre-selected group of healthy runners will straggle to a special tent staffed by Stanford University School of Medicine researchers. There, a team led by Suzanne Miller, MD, a resident in emergency medicine, will try to determine the grueling 26.1-mile race’s effect on the heart. Miller will test elite and recreational runners to determine if their hearts respond differently to a marathon. The runners will undergo a battery of medical tests to give the researchers a clear picture of the heart’s condition. They will visualize the heart with an ultrasound, measure the heart’s regularity and analyze two molecular indicators of heart damage from the blood. The Stanford team will test the runners three times: the day before the race, immediately after the finish and one day later. If abnormalities are found, repeat studies will be performed a week after the race. The examination prior to the race will include a state-of-the-art echocardiogram, an ultrasound picture of the heart. The researchers are excluding runners with risk factors for heart problems, such as high blood pressure and diabetes. Miller recruited the study participants through the race Web site. A previous study led by Euan Ashley, MD, PhD, assistant professor of cardiology at Stanford, discovered that the heart experiences fatigue and a temporary reduction in cardiac output during endurance exercise. The athletes in that study had participated in a 250-mile race and were on the verge of collapse when they finished. Miller wants to learn what happens to the hearts of ordinary athletes, who increasingly compete in marathons and triathlons. Other studies on recreational athletes found troubling, but inconclusive results. A large number of race participants, as many as half in some cases, showed signs of heart damage after running a marathon. But Miller said none of the studies did a long enough follow-up to determine if that damage was only temporary. She said this will be the first study to examine participants a week after a race for signs of heart damage. “No one has proven a marathon is bad for the heart,” said Miller. The study could provide a better picture of the heart risks recreational athletes face in these races. Pre-race heart screening, such as echocardiogram, may become a common practice as a result of investigations such as this, she said. The researchers will also try to predict athletes’ performances—their finishing times—by analyzing their hearts. A Japanese research team found that an echocardiogram could foretell the performance of elite endurance athletes, but Miller’s study will be among the first to attempt to predict the times of recreational athletes. Donald Schreiber, MD, a co-investigator in the study, believes the large amount of data they collect should allow the researchers to see subtle changes in the hearts of participants. Once the race is over, the researchers will look for trends in the data that tell them what a runner’s heart experiences after several hours of exercise and how well it recovers. “We’re going to extensively analyze the hearts of these healthy athletes to determine the effects of endurance exercise on cardiac function,” said Schreiber, an associate professor of emergency medicine.

Ewen Callaway is a science-writing intern in the Office of Communication & Public Affairs at the School of Medicine.