(RxWiki News) Getting a runner's high is the ultimate goal for marathon runners. But these runners can get a bit more than they asked for if they're not too careful.
A new study presented at a conference found proof that running in marathons could trigger pulmonary edema, where fluid builds up in the lungs.
"Strenuous activity in moderation is still good for you."
Researchers from the United States and Italy aimed to study the link between heavy exercise and pulmonary edema, which causes breathlessness and heavy cough.
In serious cases, it can also sometimes cause heart attacks or respiratory failure.
Though the study is small, the researchers analyzed 26 runners in the 2011 Steamtown Marathon in Pennsylvania.
They took chest radiographs of each runner the day before the race, and then at 19, 56, and 98 minutes after the race.
By looking at these different times, the researchers ensured that any increase in blood volume would return to normal.
Researchers brought in experts to interpret the radiograph images and score each image on the level of edema present, with 0 being no edema and 8 as having severe edema.
Two of the readers were experts in reading the films and a third was a general radiologist.
None of the readers knew at which stage the images were taken.
Though the results are still preliminary and need to be reviewed, the researchers found that about 50 percent of runners had some level of pulmonary edema about 20 minutes after the race.
Further, 20 percent of those runners had moderate to severe pulmonary edema, and an hour after the marathon was finished, pulmonary edema was still present.
Average edema scores increased from 1.5 before the marathon to 4.1, 3.7, and 2.8 units at 19, 56, and 98 minutes after the race.
"While pulmonary edema can be a negative consequence of marathon running, regular exercise can also keep you fit and healthy," said Gerald Zavorsky, PhD, an associate professor of human physiology at Marywood University.
"We do not yet know the impact of this finding on long-term health of runners."
The study was presented Sept. 3 at the European Respiratory Society's Annual Congress in Vienna, Austria.