It takes much will power, effort and perseverance to complete a marathon. Completing this type of race – all 26.2 miles of it – requires the body to be in good physical condition. While running is often considered synonymous with good health, a new study suggests that marathons could have a negative impact on the kidneys.

A Close-Up Look

This report, which appeared in the American Journal of Kidney Disease, examined the kidney health of a small number of runners in the 2015 Hartford Marathon. To accomplish this goal, the authors collected both urine and blood samples prior to the beginning of the marathon. Each volunteer was also asked to submit additional blood/urine samples after the conclusion of the race.

In both of these fluids, the researchers carefully studied several potential indicators of kidney damage, some of which are serum creatinine levels, kidney cells on microscopy, and urine proteins.

Quick Developing Problems

Surprisingly, the marathon took quite a toll on the runners kidneys. More than four-fifths (82%) of the participants exhibited clear signs of Stage 1 Acute Kidney Injury (AKI). In short, AKI occurs when the kidneys have difficulty removing waste from the bloodstream.

So what caused the runners kidney woes? As of now, the authors aren’t quite sure. Some possible explanations include a rise in core body temperature and dehydration. Alternatively, it could be that the kidneys are not sufficiently supplied with blood during marathons. The good news is that the subjects’ kidney issues dissipated two days after their marathon runs.

Dr. Chirag Parikh, the study’s senior author, stated that “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.” The Yale professor further added that “We need to investigate this further. 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.”