Completing a marathon can be triumphant — but also heart-rending, in a surprisingly literal sense. Immediately after a race, many recreational marathoners have been found to have high levels of enzymes in their blood that indicate cardiac damage. These runners have “stunned” their hearts, as some exercise cardiologists put it. Enzyme levels generally return to normal within a week or so, suggesting that hearts recover quickly, but some experts have still wondered if there are less-stressful ways to get through a marathon. For example, should nonelite runners deliberately walk part of the way?

Exercise scientists in Germany took up this question for a study published earlier this year in the Journal of Science and Medicine in Sport. They recruited 42 recreational runners training for their first marathon and then, just before the race, randomly split them into two groups. Half the runners were told to walk for a minute after roughly every mile and a half, the others to run the entire race. Everyone set their own running and walking paces.

Both groups felt some trepidation about their assignments, according to Kuno Hottenrott, a professor of sports science at Martin Luther University in Germany, who led the study. The nonstop runners “were worried that they would not be able to finish the entire race without having to walk for a bit,” he says, while the walkers fretted that their times would suffer. In fact, almost all of them finished in a little more than four hours, a relatively respectable time for nonelite runners. The walkers tended to speed up when they resumed running, producing faster average miles than those in the other group.