It's Patriot's Day, and if you're a runner, you know what that means. It's the Boston marathon! This annual race is the oldest of its kind, making it a huge item to cross off many runner's bucket lists.

For the professional marathon runners, it's a chance to win one of the most iconic races in the sport.

If you've ever run a marathon, you know the toll it can take on your body and the physical exhaustion it can cause. You're sweating, you're breathing heavy, your heart is racing.

While exercise is one of the most beneficial ways to keep your heart healthy, running a marathon can also come with some serious drawbacks - like cardiac arrest.

So, with the Boston marathon underway, we ponder the question of what marathons really reveal about heart health.

The Heart Risks of Distance Running

If you've ever tracked your heart rate during a long run, you already know it climbs. Fast. That pounding in your chest isn’t just in your head. During a marathon, your heart rate stays elevated for hours, often hanging out in the moderate to high intensity range, depending on your fitness level and race pace.

On average, most runners maintain about 70–85% of their maximum heart rate during a marathon. For many, that falls somewhere between 140–170 beats per minute, but it can vary based on factors like age, training experience, and hydration. (1)

While that’s within a reasonable aerobic range, it’s also a prolonged stressor on your cardiovascular system—especially when sustained over 26.2 miles.

Elite runners, with years of training and freakishly efficient hearts, can handle that effort with less strain. But for the average runner, especially those pushing their limits, heart rates can creep up into anaerobic zones—where the body starts to rely more on sugar than oxygen for fuel. That can lead to exhaustion, dehydration, and in rare cases, cardiac arrest.

These cases are often linked to undiagnosed heart conditions like hypertrophic cardiomyopathy - an abnormal thickening of the heart muscle - or certain types of arrhythmias - irregular heart rhythms. Most runners who experience these issues didn’t even know they had a heart condition in the first place, which is what makes it so dangerous.

Even in healthy runners, long, intense training can put strain on the heart. After long races or heavy training blocks, some runners can experience temporary inflammation of the heart muscle or changes in heart rhythm. Over time, especially in older athletes, this can raise the risk for conditions like atrial fibrillation, which can mess with your heartbeat and increase the risk of stroke.

Marathon Runner Suffers Cardiac Arrest

Sometimes, even when everything seems right, things can still go wrong. That was the case for Meghan Roth, an experienced marathon runner and coach, who went into sudden cardiac arrest just 7.4 miles into the Boston Marathon. She was healthy, trained, and prepared, but her heart had other plans.

Thanks to quick action from bystanders and medical support at the event, Meghan survived. But her story is a reminder that these things don’t only happen to out-of-shape or inexperienced runners. They can happen to anyone, even someone who’s run marathons before and knows their body well.

The Heart Benefits of Distance Running

Distance running isn't all bad though, despite some of the drawbacks. Running a marathon is a huge accomplishment, and what was once a sport for elite athletes is now a sport for anyone who has the dedication and fitness level to complete one.

It can also be very beneficial for your heart and overall health.

Training for and completing a marathon does more than just build mental toughness—it strengthens your heart, improves circulation, and helps your cardiovascular system become more efficient. Over time, runners can develop lower resting heart rates, better blood flow, and more stable blood pressure.

And it’s not just about what happens during the race. Regular endurance training is linked to a lower long-term risk of high blood pressure, high cholesterol, and heart disease. That’s huge, considering heart disease is still the leading cause of death in the U.S.

Then there’s the mental side. Running is a powerful stress reliever. It boosts endorphins, clears your head, and helps reduce anxiety, indirectly supporting your heart health by lowering stress hormones like cortisol. And when you add it all up? Studies consistently show that people who stick with aerobic activity—like running—tend to live longer and healthier lives. (2)

Tips For Race Day

When marathon morning finally rolls around, it’s easy to get swept up in the energy, adrenaline, and crowd. But even on your biggest race day, your heart still needs you to be smart and pay attention. Here are some of the best tips to keep your heart safe and strong from start to finish:

• Don’t ignore the warning signs

If you feel lightheaded, dizzy, short of breath, or experience any chest discomfort, it’s not something to push through. Slow down, walk, or stop entirely if needed. Your health is worth more than your finish time.

• Hydrate—but don’t overdo it

Yes, staying hydrated is crucial. But drinking too much water, especially without electrolytes, can dilute sodium levels in the blood and lead to hyponatremia—a serious and potentially life-threatening condition. Aim for balanced hydration with a mix of water and electrolyte-rich drinks, especially on hot days.

• Warm up and cool down

Don’t go from zero to 100 at the starting line. Give your body—and your heart—a chance to ease into the effort with a short warm-up jog or dynamic stretches. After the race, resist the urge to collapse right away. Cool down with a walk or light movement to help your heart rate come down gradually.

• Stick to your pace

The excitement of race day makes it easy to go out way too fast in the first few miles. But that can backfire quickly, especially when your heart is working overtime. Run the pace you trained for, not the one your ego or the crowd tempts you into.

Remember, finishing strong isn’t about pushing at all costs—it’s about running smart, listening to your body, and taking care of the engine that keeps you moving: your heart.

Sources

(1) Boullosa, D., Del Rosso, S., & Lepers, R. "Heart rate does not reflect the %VO2max in recreational runners during the marathon." International Journal of Environmental Research and Public Health, vol. 19, no. 19, 2022.

(2) American Medical Association, "Massive study uncovers how much exercise is needed to live longer," AMA, March 18, 2024.