People whose hearts stop functioning during or shortly after exercising are three times more likely to survive than those who have cardiac arrest unrelated to working out, researchers said.

The Amsterdam Resuscitation Study looked at 2,517 cardiac- arrest cases in the Dutch capital’s greater metropolitan area over a three-year period. Scientists found 145 of the patients were exercising during or within one hour of cardiac arrest and were mostly biking, playing tennis, working out at a gym or swimming, according to the research presented today at the European Society of Cardiology conference in Munich.

Almost half of the patients who were exercising survived the event and they had a much better prognosis than those who weren’t working out, the study said. Only 15 percent of those whose cardiac arrest wasn’t exercise-related lived, the study said. Those who were exercising were mostly young and male and suffered cardiac arrest in a public place where they were more likely to receive cardiopulmonary resuscitation, or CPR, from a bystander, according to the researchers.

“The remarkably good survival of victims of exercise- related out-of-hospital cardiac arrest can partially be ascribed to the fact that they are younger and more likely to suffer the arrest in a public location, leading to bystander CPR,” Arend Mosterd, a cardiologist at the Meander Medical Center in Amersfoot, the Netherlands, and a co-author of the study, said in a statement Sunday. “Taking these factors into account, exercise per se also contributes to a better outcome.”

A sudden cardiac arrest occurs when the heart’s electrical system malfunctions, causing the organ to stop beating. Performing CPR or using a defibrillator to shock the heart back into a normal rhythm within minutes can reverse sudden cardiac arrest.

In the study, none of the patients who were exercising and survived suffered serious neurological damage, which wasn’t the case for non-exercise related cases, Mosterd said.

“Although physical activity is the best way to promote cardiovascular health, exercise can also trigger an acute cardiac event leading to death,” Mosterd said. “These dramatic and often high-profile events, for example in soccer players, invariably lead to concerns and cast a shadow over the overwhelmingly positive effects of regular exercise.”

Fabrice Muamba, then a midfielder for the Bolton Wanderers soccer team, survived a cardiac arrest after collapsing during a game on March 17. His heart had stopped for more than an hour and he spent a month in the hospital. The 24-year-old retired this month.

Muamba still experiences abnormal heart rhythms, Sanjay Sharma, a sports cardiologist and consultant to Tottenham Hotspur, which played the Bolton team the day the footballer collapsed, said during the conference Sunday. Sudden cardiac death in athletes is rare, occurring in about one in 50,000 athletes, Sharma said. There are often no symptoms and many non- professional athletes aren’t screened, he said.

“Between one in 250 and one in 500 athletes are walking around today harboring a condition that could potentially kill them,” Sharma said.

Athletes, particularly those of African descent, can experience an abnormal thickening of heart muscle which can cause an irregular heart rhythm and lead to sudden death, John Harold, president-elect of the American College of Cardiology, said in an interview in Munich. The cause can be physiological or genetic, and athletes should be screened for it, he said.

“You shouldn’t have soccer players collapsing on the field,” Harold said. “Screening should happen a lot earlier.”