Are Too Many Marathons Bad for Your Heart?
For years the marathon has been held up as the ultimate symbol of fitness, discipline and mental toughness. Completing 26.2 miles is often seen as proof that someone is exceptionally healthy, especially when compared to a sedentary lifestyle or obesity. Many people quite reasonably think that if running is good for you then running a lot must be even better. Recently however a growing number of doctors and cardiologists have begun to question whether repeatedly running marathons is actually good for long term health, particularly heart health, and the findings are making a lot of people uncomfortable.
This is not an argument against exercise. Far from it. Regular physical activity is one of the most powerful tools we have for reducing the risk of heart disease, type 2 diabetes, many cancers, depression and early death. Moving your body consistently is non negotiable for good health and quality of life and that point is not up for debate. The question being raised is whether extreme endurance exercise performed year after year pushes the body beyond what it is designed to tolerate safely over decades.
Exercise Is Medicine but Dose Matters
One of the most important principles in medicine is that dosage matters. Water is essential for life but drink far too much in a short period and it can be fatal. Exercise works the same way. Small to moderate doses improve health dramatically. Excessive doses especially without adequate recovery may have unintended consequences. This idea is becoming increasingly accepted in cardiovascular research.
Large population studies consistently show that people who engage in moderate exercise live longer than those who are inactive. The biggest drop in health risk happens when someone goes from doing nothing to doing something. Walking briskly, strength training, cycling, swimming and short bursts of higher intensity work all provide enormous benefits. Interestingly the curve flattens out after a certain point. Doing more and more exercise does not always lead to proportionally greater health benefits and in some cases may reverse them.
The Physical Demands of Marathon Running
Training for a marathon is not the same as going for a jog a few times a week. It requires months of high mileage, long runs lasting several hours and significant cumulative stress on the body. During a marathon the heart must pump large volumes of blood continuously for an extended period. Heart rate remains elevated for hours and cardiac output is pushed close to maximum for far longer than it would be during most other forms of exercise.
From a mechanical perspective this places enormous strain on the heart muscle. Studies using cardiac imaging have shown that after endurance events such as marathons and ultramarathons some athletes experience temporary changes in heart function. These include reduced pumping efficiency of the right ventricle and elevated markers of cardiac stress in the blood. While these changes often resolve within days or weeks repeated exposure over many years may lead to structural adaptations that are not always beneficial.
What Cardiologists Are Now Seeing
A growing body of evidence suggests that chronic extreme endurance exercise may contribute to changes in heart structure and electrical signalling. Some cardiologists have observed higher rates of atrial fibrillation in long term endurance athletes compared to the general population. Atrial fibrillation is an irregular heart rhythm that increases the risk of stroke and heart failure.
There is also evidence that repeatedly forcing the heart to operate at very high outputs for prolonged periods can lead to enlargement of the heart chambers and thickening of the heart walls. While some enlargement is a normal adaptation to training excessive changes may disrupt the heart’s electrical system and impair efficient pumping.
Dr James O’Keefe and Dr Carl Lavie from leading cardiovascular research institutions have been particularly vocal on this issue. They argue that the human heart evolved for intermittent physical demands rather than hours of sustained maximal output. According to their research the heart appears to respond best to short bursts of effort combined with ample recovery rather than chronic endurance stress performed year after year.
The Human Body Is Built for Variety
From an evolutionary standpoint humans were never designed to run continuously for several hours on a regular basis. Our ancestors moved frequently but in varied ways. Walking long distances, lifting, climbing, sprinting briefly to escape danger or hunt and then resting. This pattern of movement aligns far more closely with modern approaches like strength training, interval training and mixed modal exercise.
Mentally this matters too. Long endurance training requires a level of monotony and time commitment that many people struggle to sustain without burnout. Chronic fatigue, overuse injuries, hormonal disruption and immune suppression are all more common in athletes who push high volumes of endurance training without sufficient recovery.
Being Active Versus Being Extreme
It is important to separate the idea of being active from the idea of being extreme. Being active is unequivocally beneficial. Sitting less, moving more, building muscle and maintaining cardiovascular fitness should be priorities for everyone. Extreme endurance exercise is something different altogether.
Many people assume the comparison is between marathon running and obesity. In reality the healthier comparison is between marathon running and consistent moderate training that includes strength work, mobility, aerobic conditioning and short bursts of higher intensity. The latter approach delivers most of the benefits with far less risk and far greater sustainability over a lifetime.
A Personal Trainer’s Perspective
As a personal trainer my role is not to chase impressive sounding goals at the expense of long term health. My job is to help people achieve and maintain a healthy weight, strong body and resilient cardiovascular system for decades not just for a race day photo.
Over the past decade I have helped several clients achieve the dream of completing a marathon. For many it was a once in a lifetime goal and I am proud to have supported them through that journey. Crucially most of those clients did not go on to run marathons year after year. They returned to more balanced training that supported overall health and injury prevention.
If a client came to me today with the intention of running multiple marathons every year indefinitely I would have an honest conversation with them about the emerging evidence. I would not forbid it but I would strongly encourage a broader view of fitness that prioritises heart health, strength, recovery and longevity.
Short Bursts and Long Term Health
Research increasingly supports the idea that shorter bouts of higher intensity exercise combined with strength training provide exceptional cardiovascular benefits. Interval training has been shown to improve aerobic capacity, insulin sensitivity and fat metabolism efficiently. Strength training improves bone density, muscle mass, joint health and metabolic rate which are all critical for ageing well.
This style of training places stress on the heart in a way it seems better equipped to handle. Short bursts of effort followed by recovery allow the cardiovascular system to adapt without prolonged overload. Mentally it is also more engaging and far easier to fit into a busy life.
So Should Anyone Run a Marathon
Running a marathon is not inherently dangerous for a healthy well prepared individual. For many it can be a meaningful personal challenge and a powerful achievement. The issue is repetition and volume over many years without adequate balance.
If someone truly wants to run a marathon or a full distance triathlon it may be best viewed as a limited event rather than a permanent lifestyle. Completing one or a few and then transitioning to safer more balanced exercise patterns may offer the best of both worlds.
A Smarter Approach to Fitness
The goal of exercise should be to enhance life not dominate it or shorten it. Training should leave you feeling energised capable and resilient not chronically exhausted injured or anxious about missing sessions.
A well designed fitness programme includes resistance training, cardiovascular conditioning, mobility work and rest. It respects the fact that the body thrives on variety and recovery. It recognises that more is not always better and that consistency beats extremes every time.
If you are currently training for endurance events or considering them it is worth reflecting on your long term goals. Are you training for a finish line or for a lifetime of health. Both can coexist when approached intelligently.
Final Thoughts and Call to Action
Exercise remains one of the most powerful tools we have for preventing disease and improving quality of life. The emerging conversation around marathon running is not about discouraging movement but about encouraging smarter movement.
If your goal is to be lean, strong, healthy and active well into later life then balanced training is the answer. Short intense efforts, strength work and regular movement outperform extreme endurance training when it comes to sustainability and long term heart health.
If you want guidance on how to train in a way that supports your heart, your joints and your future then now is the time to act. Get professional support. Train with purpose. Respect recovery. Build a body that works for you for decades to come and not just for one exhausting race day. Book a personal training taster session today.