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Is Running a Marathon Good or Bad for Your Heart?
Short answer: for most people, marathon training and running are more beneficial than harmful for heart health, when done progressively, with appropriate screening, and in the right context.
Where people get tripped up is assuming that because running is “healthy,” more is always better, or that marathons are either inherently dangerous or universally protective. The truth, as usual, sits in the middle.
Marathon running or even ULTRA marathons have grown dramatically in popularity over the last decade, across all age groups. With that growth has come increased attention on rare but highly publicized cardiac events during races. This has led many runners to wonder whether pushing the body to this extreme is actually good for the heart, especially as they get older.
How the Heart Adapts to Endurance Training
What we know is that the heart is a muscle, and like other muscles, it adapts to the stress placed on it. Endurance training leads to well-documented cardiovascular adaptations, including increased stroke volume, reduced resting and submaximal exercise heart rate, improved oxygen utilization (VO₂ max), and lower blood pressure (Predel, 2014). These changes allow the heart to pump more blood with fewer beats, improving overall efficiency.
This adaptation is often referred to as “athlete’s heart.” It is a non-pathological enlargement of the heart that occurs in response to long-term endurance training and is associated with improved cardiac function, not disease (Lauschke & Maisch, 2009).
One reason this adaptation can cause concern is that it may resemble hypertrophic cardiomyopathy (HCM) on imaging, a genetic condition that is a leading cause of sudden cardiac death in young athletes (Day & Thompson, 2010). Distinguishing between the two is critical and highlights why appropriate screening matters before engaging in high-volume endurance training.
Acute Cardiac Stress During a Marathon
During a marathon, the cardiovascular system is placed under significant acute stress. Runners rely almost entirely on the aerobic energy system, often sustaining high percentages of their VO₂ max for prolonged periods (Hagerman, 1992).
Studies examining heart function immediately after marathons frequently report transient electrical changes on ECGs and short-term elevations in cardiac biomarkers such as troponin and brain natriuretic peptide (BNP) (Leers et al., 2006; Kim et al., 2014).
This is where interpretation matters. Troponin is commonly used in clinical settings to diagnose myocardial infarction, but post-marathon elevations in healthy runners are typically modest and return to baseline within 24 hours (Leers et al., 2006). These findings suggest temporary cardiac stress rather than permanent damage.
BNP elevations follow a similar pattern, reflecting transient changes in ventricular pressure and workload, particularly in older runners (Kim et al., 2014). In healthy individuals, these responses appear to be part of a normal physiological stress-and-recovery cycle.
Age, Risk, and Marathon Running
Age plays a major role in how cardiac risk is distributed among marathon runners. In younger athletes, rare cardiac events are more often linked to inherited structural abnormalities such as HCM (Webner et al., 2012).
In runners over 40 to 45 years old, the most common cause of marathon-related cardiac events is coronary artery disease (CAD), often due to underlying atherosclerosis (Day & Thompson, 2010). Autopsy data from marathon-related fatalities consistently show CAD as the predominant finding in older runners (Mathews et al., 2012).
Importantly, this does not mean older adults should avoid marathon running. In fact, regular endurance exercise is associated with improved lipid profiles, lower blood pressure, reduced sympathetic nervous system activity, and decreased risk of early cardiovascular mortality (Leosco et al., 2013; Albert et al., 2000).
For many individuals, endurance training is protective, particularly when introduced gradually and paired with appropriate medical oversight.
High-Volume Endurance Training and Long-Term Effects
A more controversial area of research involves the effects of very high volumes of endurance exercise performed over many years. Some studies suggest that long-term ultra-endurance athletes may exhibit increased arterial stiffness and reduced arterial compliance compared to moderately active individuals (Burr et al., 2013; Vlachopoulos et al., 2010).
Increased arterial stiffness can theoretically contribute to higher cardiovascular strain over time, even in highly trained athletes.
However, these findings are often misinterpreted. They do not establish causation, and they largely apply to individuals performing extreme volumes of endurance exercise over decades. They also do not negate the many functional benefits observed in these athletes.
The takeaway is not that marathon running is harmful, but that there may be a point where additional volume offers diminishing cardiovascular returns, especially if recovery and overall stress management are inadequate (Predel, 2014).
Screening and Preparation Matter
This nuance is particularly important for non-elite and first-time marathoners. Research shows that most serious race-day cardiac events occur in individuals with undiagnosed underlying conditions or inadequate preparation, not because marathon running itself is inherently dangerous (Webner et al., 2012).
Risk increases when runners progress too quickly, ignore warning signs such as chest pain or dizziness, or begin intense endurance training later in life without screening.
Pre-participation screening can be as simple as a detailed medical history and resting ECG, and in some cases may include an exercise stress test to evaluate for coronary artery disease (Smith et al., 1989; Day & Thompson, 2010). These screenings are particularly relevant for runners over 40 or those with known cardiovascular risk factors.
Elite marathon runners generally face lower risk of sudden cardiac arrest during races because their hearts and vascular systems have adapted over years of progressive training. At the same time, lifelong high-volume training may increase susceptibility to arterial stiffness and aortic changes, reinforcing the idea that even in elite populations, cardiovascular adaptations are complex rather than universally positive or negative (Carrick-Ranson et al., 2014).
So… Is Marathon Running Good or Bad for Your Heart?
So, is marathon running good or bad for your heart? For most people, the benefits of endurance training outweigh the risks when training is approached intelligently.
Marathon training can improve cardiovascular efficiency, lower resting heart rate and blood pressure, enhance metabolic health, and reduce long-term disease risk. The risks that do exist are rare and are most often tied to pre-existing conditions, poor preparation, or lack of screening.
The most important takeaway is that marathon running is not inherently protective or harmful. It depends on the individual. Age, health history, training progression, recovery, and life stress all influence how the heart responds.
If you’re untrained, jumping straight into marathon training is not a smart move. If you’re older, screening becomes more important, not less. And if you’re well-trained and supported, marathon running can be a powerful tool for long-term cardiovascular health.
A Personal Note on Bias and Fitness Messaging
Interestingly, a version of this article started as a term paper I wrote during undergrad as an Exercise Science student, and at the time, I hated running. I went into the research convinced I was going to prove that running was bad for you.
Looking back, I can see how much of that bias came from how I personally experienced running: as punishment, as something tied to weight loss, or as something you “had” to do rather than chose to do.
What that experience taught me, and what I still see play out online, is how easy it is to consume information that reinforces what we already believe. That’s why this topic matters so much.
When fitness content is extreme, one-sided, or framed as “always” or “never,” it’s usually a red flag. Real science almost always lives in the gray.
Coaching, Context, and the Right Approach
If you’re feeling inspired by the idea of running or unsure how to start safely, that’s exactly where individualized coaching can make a difference!
At LVLTN, we work with beginners building their first consistent running routine, experienced runners training for races, and people who simply want to improve heart health without pushing into extremes.
Coaching helps take the guesswork out of progression, recovery, and intensity so training supports your life and your health, not the other way around.
Want to learn how working with an LVLTN coach can help you reach your goals—and stay there? Start with a free LVLTN Blueprint Session.
It’s your personalized roadmap to clarity, consistency, and real results. You just need to fill out a quick application, then our team will review it and reach out with a link to schedule your session within 24 hours. Get started by clicking here!
References
Albert CM, Mittleman MA, Chae CU, et al. Triggering of sudden death from cardiac causes by vigorous exertion. N Engl J Med. 2000.
Burr JF, Drury CT, Phillips AA, et al. Long-term ultra-marathon running and arterial compliance. J Sci Med Sport. 2013.
Carrick-Ranson G, Hastings JL, Bhella PS, et al. The effect of lifelong exercise dose on cardiovascular function. J Appl Physiol. 2014.
Day SM, Thompson PD. Cardiac risks associated with marathon running. Sports Health. 2010.
Hagerman FC. Energy metabolism and fuel utilization. Med Sci Sports Exerc. 1992.
Kim YJ, Shin YO, Lee JB, et al. Effects of ultra-endurance running on cardiac markers. Eur J Sport Sci. 2014.
Lauschke J, Maisch B. Athlete’s heart or hypertrophic cardiomyopathy? Clin Res Cardiol. 2009.
Leers MP, Schepers R, Baumgarten R. Effects of long-distance running on cardiac markers. Clin Chem Lab Med. 2006.
Leosco D, Parisi V, Femminella GD, et al. Exercise training and cardiovascular adrenergic regulation. Front Physiol. 2013.
Mathews SC, Narotsky DL, Bernholt DL, et al. Mortality among marathon runners, 2000–2009. Am J Sports Med. 2012.
Predel HG. Marathon running: cardiovascular adaptation and risk. Eur Heart J. 2014.
Smith GS, Vacek JL, Wilson DB, et al. Exercise-induced ECG changes in marathon runners. Am Heart J. 1989.
Vlachopoulos C, Kardara D, Anastasakis A, et al. Arterial stiffness in marathon runners. Am J Hypertens. 2010.
Webner D, DuPrey KM, Drezner JA, et al. Sudden cardiac arrest in U.S. marathons. Med Sci Sports Exerc. 2012.
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