A trio of recent medical journal reports offer multiple assurances to veteran runners. The papers explore links between endurance training/racing and heart health.
The subject has been top of mind for many runners since 1984 when famed book author Jim Fixx (The Complete Book of Running) died at age 52 while running on a rural road in Vermont.
In the subsequent four decades, infrequent-but-headline-grabbing deaths at marathon races, occasional studies on “excessive exercise,” and various blogs and YouTube videos have kept some runners (and their families) on edge.
The biggest of the new papers, called RACER 2 for easy identification (Race Associated Cardiac Event Registry),1Kim, J. H., Rim, A. J., Miller, J. T., Jackson, M., Patel, N., Rajesh, S., Ko, Y.-A., DiGregorio, H., Chiampas, G., McGillivray, D., Holder, J., & Baggish, A. L. (2025). Cardiac Arrest During Long-Distance Running Races. JAMA. https://doi.org/10.1001/jama.2025.3026 was published in the prestigious Journal of the American Medical Association (JAMA). It tallied up cardiac arrests and deaths among an astounding 9,311,597 marathon and half-marathon finishers during the years 2010 to 2023.
When analyzing the recent period, as opposed to an earlier report from RACER 1 (2000 to 2009),2Kim, J. H., Malhotra, R., Chiampas, G., d’Hemecourt, P., Troyanos, C., Cianca, J., Smith, R. N., Wang, T. J., Roberts, W. O., Thompson, P. D., & Baggish, A. L. (2012). Cardiac Arrest during Long-Distance Running Races. New England Journal of Medicine, 366(2), 130–140. https://doi.org/10.1056/nejmoa1106468 the JAMA paper concluded: “The risk of cardiac death during marathons and half-marathons has declined markedly by approximately 49%.”
The Research Marathon
The RACER papers were conceived and initiated by a then-young Boston cardiologist and frequent marathoner named Aaron Baggish. Baggish has a marathon best of 2:49, and went on to become the Boston Marathon’s co-medical director for a decade before moving to Lausanne, Switzerland, in 2022.
Baggish is also co-author of another recent article, along with a lengthy list of other endurance exercise cardiologists widely recognized as global experts. Their article, “Coronary atherosclerosis in athletes: emerging concepts and preventive strategies,”3Guido Claessen, Thijs M H Eijsvogels, Albert, C. M., Baggish, A. L., Levine, B. D., Eloi Marijon, Michos, E. D., & Gerche, A. L. (2025). Coronary atherosclerosis in athletes: emerging concepts and preventive strategies. European Heart Journal. https://doi.org/10.1093/eurheartj/ehae927 appeared in the European Heart Journal. They concluded that while there’s evidence of coronary disease in some groups of endurance athletes, the data continues to support that “higher levels of fitness are associated with a markedly attenuated incidence of coronary events regardless of the severity of coronary disease.”
An Italian medical research group covered similar terrain in The International Journal of Cardiology,4Guarnieri, G., Pozzi, F. E., Conte, E., Righetto, M., Bartorelli, A., & Andreini, D. (2025). Extreme endurance training and coronary artery disease: A systematic review and a meta-analysis. International Journal of Cardiology, 429, 133172. https://doi.org/10.1016/j.ijcard.2025.133172 reporting on “Extreme endurance training and coronary artery disease: A systematic review and a meta-analysis.” Like Baggish et al, they found evidence of coronary atherosclerosis in some endurance athletes.
But they also reached a similar conclusion: “This increased prevalence of coronary atherosclerosis does not come with a higher presence of high-risk plaques. Additionally, our research shows that endurance athletes do not have a higher prevalence of obstructive plaques compared to the controls.”
The RACER 2 analysis produced reams of specific data regarding the risks of cardiac arrest in half marathons and marathons. Some highlights:
- The rate of cardiac arrests has remained relatively stable at 0.54 per 100,000 participants in RACER 1, and 0.60 in RACER 2
- Men are much more likely than women to suffer a cardiac arrest in races, at a rate of 1.12 per 100,000 vs 0.19
- The marathon is more dangerous than the half-marathon, with 1.04 cardiac arrests per 100,000 vs 0.47
- In RACER 2, there were 176 documented cardiac arrests among the 29 million + finishers, a rate of 1 per 166,167 runners
- In RACER 2, there was a 66% survival rate among stricken runners. This marked a big improvement over the 29% survival rate in RACER 1, probably due to increased bystander CPR and on-course defibrillators
In fact, first author Jonathan H. Kim noted: “We found that every one of those survivors got hands-on cardiopulmonary resuscitation and the vast majority also had immediate access to an automated external defibrillator.”
Behind The Scenes At The Boston Marathon
Boston-based athletic trainer Chris Troyanos has worked on the Boston Marathon’s medical team for 49 years, 28 as the medical coordinator. According to Troyanos, there will be 1800-1900 medical personnel at the marathon this year, roughly half out on the course.
There are 26 medical tents along the course, “back loaded” so that there are more over the second half. Each has two “Proceed Out” teams on gators that roam the course for a half mile in both directions from the nearest medical tent. The teams are equipped with AED defibrillators, and communication that links them with the marathon medical coordinators and EMS Emergency Services.
Troyanos remembers the moment in 2010 when he and Aaron Baggish had a light-bulb moment. “We knew we were doing everything we could with our medical volunteers,” he says. “But we suddenly realized that we weren’t harnessing the multiplier force of all the runners themselves, as well as the spectators on the course.”
They quickly began organizing a CPR educational program. It now includes information that is emailed each year to all runners, as well as a CPR booth at the Marathon Expo. There, runners and their families can practice CPR on an electronically–equipped mannequin that teaches the correct pressure and frequency to apply when performing CPR. Each year at the Expo, about 1200 runners and others have utilized this instruction.
“We’ve worked hard on providing great medical support and educating runners,” says Troyanos. “But we’ve also been very lucky. We haven’t had a cardiac arrest death at Boston since 1996.”
Run Long, Run Healthy
Runners are the first line of medical protection and safety in any road race. Be prepared. Some guidelines:
1: Don’t run if you have had any recent symptoms yourself
This of course is the first rule of healthy running: Listen to your body.
Before a long race like a marathon or half-marathon, it applies especially to any recent viruses, coughs/congestion in the chest (as opposed to a simple head cold), and pains in the chest or arm.
2: Learn hands-only CPR—and make sure your cheer squad knows it too
You never know when you or spectators will have a chance to assist a stricken runner, so you should always be prepared, and mentally rehearsing the actions you may have to take.
A decade ago, the Boston Marathon and cardiologist Aaron Baggish created a special Boston Marathon video on YouTube with key information about hands-only CPR. Parts of the video are old and grainy, but the advice is still good. Watch it. It will only take four minutes of your time.
3: Don’t sprint for the finish line
(Unless someone is holding up a $50,000 check for you.) It’s much smarter and healthier to finish your marathon at a steady, controlled pace.
Marathon studies, including RACER 1 and RACER 2, have shown that there are a disproportionate number of cardiac arrests towards the end of marathons. Don’t go for broke at the end. Take it easy and enjoy your accomplishment.
4: Be careful with your use of stimulants
Many marathon runners drink coffee before their races, and often take caffeine gels on the course. Okay, this isn’t likely to change. Caffeine is a legal performance-enhancer that lowers your perceived effort while running. But don’t overdo caffeine intake.
The authors of RACER 2 reported “an unexpected observation” that four runners who died of cardiac arrest had a postmortem toxicology test that “revealed the presence of stimulants (caffeine, amphetamines, and/or pseudoephedrine).”
