The physical stress from running a marathon could cause short-term kidney injury, according to researchers.

The Yale University researchers note that although the kidney injury resolved itself within a few days after the marathon, its occurrence could raise questions regarding the effects of repeated strenuous activity over time, especially in warm climates.

In their study, published recently in the American Journal of Kidney Diseases, the research team—led by Professor of Medicine Chirag Parikh, MD—studied a small group of participants in the 2015 Hartford Marathon.

The team collected blood and urine samples before and after the event and analyzed a variety of markers of kidney injury, including serum creatinine levels, kidney cells on microscopy, and proteins in urine. They found that 82% of the runners that were studied showed Stage 1 Acute Kidney Injury (AKI) soon after the race. AKI is a condition in which the kidneys fail to filter waste from the blood, according to a media release from Yale University.

“The kidney responds to the physical stress of marathon running as if it’s injured, in a way that’s similar to what happens in hospitalized patients when the kidney is affected by medical and surgical complications,” Parikh says, in the release.

Potential causes of this injury, according to the researchers, could be the sustained rise in core body temperature, dehydration, or decreased blood flow to the kidneys that occur during a marathon.

“We need to investigate this further,” Parikh adds. “Research has shown there are also changes in heart function associated with marathon running. Our study adds to the story—even the kidney responds to marathon-related stress.”

[Source(s): Yale University, Science Daily]