Cardiac Deaths During Marathons Are Becoming Rare

Are long-distance races getting safer? A massive new study says yes—with one critical factor leading the charge.

An updated analysis from the Race Associated Cardiac Event Registry (RACER) looked at cardiac arrests that occurred during US marathons and half-marathons between 2010 and 2023, aiming to track how often they happen, who’s most at risk, and how survival rates have changed over time.

Over the 13-year span from 2010 to 2023, there were 176 documented cardiac arrests among more than 29 million US marathon and half-marathon finishers—an incidence of just 1 in every 166,667 runners. Of those, 117 individuals survived, resulting in a 66% survival rate. This marks a dramatic improvement from the 29% survival rate reported in the earlier RACER study (2000–2009), suggesting that enhancements in emergency preparedness—especially widespread availability of bystander CPR and on-course defibrillators—have significantly improved outcomes.

The risk was notably higher in men (1.12 per 100,000) than in women (0.19 per 100,000) and in marathoners (1.04 per 100,000) compared to half-marathoners (0.47 per 100,000).

Of the cases with confirmed medical causes, coronary artery disease (CAD) was the most common culprit, accounting for 40% of arrests—especially among older runners. Hypertrophic cardiomyopathy (an enlarged heart), previously thought to be the leading cause, was found in only 7% of cases. Unexplained sudden arrhythmic death and exertional heat stroke also appeared but were less common. In survivors, rapid CPR and immediate AED use were nearly universal, while delayed response or non-shockable heart rhythms were linked to fatal outcomes.

What this means for runners

Cardiac arrest risk during races is low, but thanks to better medical planning and faster responses, your chances of surviving one have more than doubled since 2000. That’s a huge win for runners, race directors, and medical teams.

RELATED ARTICLE: Is Running Good For You? 14 Health Benefits Of Running​

🎧 New Podcast Episode: The Only Running Shoe Guide You Need in 2025

👟 From carbon plates to sky-high foam stacks, the running shoe world has never been more crowded—or confusing. In this week’s episode of the Marathon Handbook Podcast, we break down the chaos and help you build your ideal shoe rotation.

Plus, find out what’s on our feet right now—and what might be next for yours 👀🔥.

Or listen and subscribe to the show wherever you get your podcasts:

Want to Run Faster? Lift Heavy and Jump

Like most runners, I could be better about getting to the gym. But new evidence says if you are going to strength train, make it count. Not all types of training are created equal for improving running performance.

A new meta-analysis crunched data from 38 studies and nearly 900 runners (middle- and long-distance runners racing the 800m to the marathon distance) to ask a key question: Which types of strength training improve running performance? The researchers looked at heavy strength training, plyometrics, submaximal lifting, and combos of all three—and how they affect everything from VO₂max to time trial results.

Researchers grouped strength training programs into:

• High load: Heavy lifting at ≥80% of 1-rep max
• Plyometrics: Jump training with bodyweight or light loads
• Submaximal load: Moderate weight, high-velocity lifting
• Combined: A mix of the above training methods

Classic performance indicators like VO₂max, lactate threshold (MMSS), vVO₂max (the speed at VO₂max), sprint capacity, and actual running performance (time trials or time to exhaustion) were measured before and after training.

High-load strength training significantly improved running performance, with the strength of the effect being rated as moderate. Combined strength training (e.g., heavy lifting plus plyos) had an even bigger impact, with the strength of the effect being considered large.
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What didn’t move the needle? VO₂max, vVO₂max, lactate threshold (MMSS), and sprint capacity were unchanged across all strength training types. Despite past hype for this type of training, plyometric training alone didn’t significantly boost running performance.

What this means for runners

Strength training improves running not by making your heart or lungs stronger—but by improving neuromuscular efficiency, force production, and running economy. A mix of heavy resistance training and plyometrics gives you the best bang for your buck. Just doing bodyweight jumps likely isn’t enough on its own. If you're only doing bodyweight strength or skipping lifting entirely, you're leaving speed on the table. Add heavy lifts—and ideally some plyos—to your weekly plan to run stronger, longer, and faster.

RELATED ARTICLE: 15 Plyometric Exercises for Runners: Boost Your Power & Performance​

💙💛 Come And See Us In Boston!​

Marathon Handbook invites you to an intimate live show on Saturday, April 19, 2025, from 5:30 PM to 7:30 PM.

Join the Marathon Handbook team as they dive deep into the lore, current state, and reality of running the Boston Marathon and how Boston runners can leverage the latest sports science in their marathon efforts on Monday.

A Q+A session will follow the talk, and then drinks and snacks will be provided with some time to hang out with the panel and attendees.

Each attendee will get a gift bag with some event-only merch and giveaways.

Seating is limited, so be sure to RSVP right now!

Is Your DNA Built For Distance?

Endurance performance is traditionally built on three core pillars: VO₂max, lactate threshold, and running economy. But researchers are now proposing a fourth: physiological resilience—your body’s ability to maintain output even as fatigue sets in.

A new review explores how genetic differences may influence all four pillars, helping explain why some runners adapt faster, fatigue slower, or stay healthier under heavy training loads.

Published in Genes, the review pulls together a wide range of studies linking genetic variants—changes in DNA that can be inherited or occur spontaneously and lead to variations in traits or even diseases—to endurance performance. It covers genes involved in oxygen delivery, fat metabolism, muscle composition, injury risk, and even caffeine response and sleep—all of which could affect how you train and race. Things might get a bit nerdy here…but bear with me!

Oxygen utilization

• ACE (Angiotensin-Converting Enzyme): The I allele is associated with lower ACE levels, better vasodilation, and improved oxygen transport—common in endurance athletes. D allele carriers may struggle more to improve VO₂max.

• VEGFA, NOS3, BDKRB2: These genes regulate blood vessel growth and nitric oxide production. Favorable variants increase capillarization and muscle blood flow—boosting oxygen delivery during hard efforts.

Translation: If you carry these "aerobic-friendly" variants, your heart and muscles may naturally become more efficient with training. If not, VO₂max gains might come slower, and you may need longer to adapt.

Fuel utilization

• MCT1: Encodes a lactate transporter in muscle. Some variants help shuttle and reuse lactate more efficiently, extending how long you can go hard before fatiguing.

• PPAR family (PPARA, PPARD, PPARGC1A): These regulate fat oxidation and mitochondrial biogenesis. Endurance athletes often carry versions that favor more efficient use of fat and oxygen at high effort levels.

Translation: If you’re a “fat burner” at higher intensities, you’ll spare glycogen and last longer before bonking. If your genes aren’t as favorable, more low-intensity training might help boost this metabolic flexibility.

Muscle fiber type

• ACTN3 (R577X): The XX genotype lacks a key fast-twitch muscle protein, often leading to more fatigue-resistant fibers and better endurance economy—but also more muscle soreness and slower recovery post-race.

• COL5A1: Influences tendon stiffness. The TT genotype is linked to better running efficiency and fewer soft tissue injuries—great for logging big miles.

Translation: Runners with favorable ACTN3 or COL5A1 variants may move more efficiently or be less prone to injuries. Others might benefit more from strength work or recovery focus to compensate.

Genes for resilience

• BDNF (Brain-Derived Neurotrophic Factor): A key gene for neuromuscular communication and fatigue resistance. Some variants boost brain plasticity and endurance-related brain function.

• COMT: Modulates dopamine in the brain. The Val allele may enhance stress resilience and focus during long or grueling races.

Translation for runners: If you find yourself staying mentally sharp and resilient late in long runs, thank your genes. If not, mental training, fueling, and pacing strategies may matter even more.

Caffeine and sleep genes

• CYP1A2: Fast metabolizers (A/A genotype) see bigger performance boosts from caffeine. Slow metabolizers (C/C) may get jittery or see worse performance at higher doses.

• CLOCK and BDNF: Variants here influence your body’s circadian rhythm and sleep recovery. If your genes favor a night-owl rhythm, early morning runs might feel harder—and affect recovery.

What this means for runners

Knowing your likely strengths (VO₂max responder? Efficient lactate user? Tough under fatigue?) can help tailor your training. Some genes make you more prone to muscle damage or mental fatigue. You may need to adjust nutrition, sleep habits, or recovery time accordingly.

Genetics isn’t destiny—but it’s definitely data. This emerging science doesn’t replace smart training, but it could help understand or refine it. If you’ve had a genetic test, compare your results to the genes above. If you haven’t, maybe now is the time. And if you couldn’t care less and would rather focus on hard, consistent training…more power to you!

RELATED ARTICLE: How Much Does Our Genetics Affect Our Running Potential?​

Here's what else you would have received this week if you were a subscriber to the complete, full-text edition of “Run Long, Run Healthy.” SUBSCRIBE HERE.

• Does Vitamin D Deficiency Affect Your Running Heart?

• Does a Massage Gun Actually Help After a Run?

• Low Calories? Don’t Skip the Carbs.
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​Thanks for reading. As always—Run Long, Run Healthy
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~Brady~