Marathon Running Temporarily Stresses Kidneys, Digestive System

Sex and age do not seem to play a role in post-race organ injury

Rockville, Md.-Marathon running, even in recreational athletes, can cause substantial stress on gastrointestinal system and kidneys, according to a new study conducted at the 2024 Boston Marathon. The findings were published in the Journal of Applied Physiology and the paper has been chosen as an APSselect article for December.

The Boston Marathon, first run in 1897, is the oldest annual marathon in the world. With some of the strictest qualifying times, the marathon is seen as "the pinnacle performance for endurance athletes." The training needed to successfully run a marathon is beneficial to the musculoskeletal system and the heart. But the amount of time and energy needed to complete 26.2 miles puts high stress on organ systems as well.

In this study, researchers examined blood and urine samples of 60 "qualified, competitive, yet nonelite" runners of the 2024 Boston Marathon before and after the race. The runners answered questions about gastrointestinal issues they experienced as they ran (e.g., reflux, heartburn, stomach cramps, vomiting, diarrhea) and other symptoms such as muscle cramps, headache, thirst, dizziness and fever. The volunteers were almost evenly divided between men and women and were categorized by age.

The researchers observed substantial increases in several biomarkers of organ stress after the race. For example, 75% of the study participants showed elevated levels of intestinal fatty acid binding protein, a marker of intestinal barrier injury. Nearly all the runners had increased creatinine levels, a sign of kidney stress. Past research has shown that these markers return to normal levels within 24 hours of completing a marathon in most participants.

Notably, there was no difference between males and females in the gastrointestinal symptoms runners encountered, or in how well hydrated they were during and after the marathon. In addition, neither biological sex nor age were contributing factors in post-race kidney function either.

Weather conditions on race day were around 66 degrees F with a relative humidity of 47%. The researchers noted that the warm day, in addition to the high percentage of downhill running, likely led to more extreme physiological responses than might be seen in cooler temperatures and a flatter course.

"These findings should be considered when designing interventions aimed at minimizing various gastrointestinal and renal-related health complications associated with marathon running to promote both health and performance in recreational, competitive marathon runners," the researchers wrote.

Read the full article, "Biomarkers of Organ Stress and Injury Following the Boston Marathon." It is highlighted as one of this month's "best of the best" as part of the American Physiological Society's APSselect program. Read this month's selected research articles.  

NOTE TO JOURNALISTS: To schedule an interview with a member of the research team, please contact APS Media Relations or call 301.634.7314. Find more research highlights in our Newsroom.  

Physiology is a broad area of scientific inquiry that focuses on how molecules, cells, tissues and organs function in health and disease. The American Physiological Society connects a global, multidisciplinary community of more than 10,000 biomedical scientists and educators as part of its mission to advance scientific discovery, understand life and improve health. The Society drives collaboration and spotlights scientific discoveries through its 16 scholarly journals and programming that support researchers and educators in their work.