How to Train a Runner’s Heart

Nancy Wells crossed the finish line of the 2025 Glass City Half Marathon in Toledo, Ohio, feeling elated. That in itself wouldn’t be unique—for one, the now 55-year-old has run over 60 marathons and half marathons in the past two decades. In fact, at 2:41:26, this was the slowest she had ever run the distance—and for someone as competitive as her, of course, she’s painfully aware of that.

What made crossing this finish line special was that it’s the very race during which she had suffered a heart attack a year earlier.

In 2024, Wells was planning to run the full marathon, but the Ohio winter, coupled with her busy work schedule, derailed her training. So she decided to run the half marathon instead. Still, the morning of the race, something didn’t feel right. At first, Wells chalked it up to the muggy late-April weather and decided to ease into the race more so than usual. But she found it took all her energy to get through the first two miles, which wasn’t normal. Then there was this weird chest pressure. She slowed to a walk for a bit, then called her husband to tell him she wasn’t feeling well. The last thing she remembers is making a turn at about 4.5 miles. Around midnight, she woke up in a hospital with a tube down her throat.

She was told her heart had stopped beating.

Luckily for Wells, a retired nurse running nearby was able to perform CPR on the course soon after she collapsed.

What followed were four days in a hospital, a procedure to place an artery stent (a flexible tube that helps open a narrowed vessel and increase bloodflow), and a supervised program of cardiovascular rehab. Once her heart’s ability to pump blood had improved to within normal range, she began thinking about running again—and finishing the race.

For most cardiac patients, aerobic exercise is a crucial component of ongoing rehabilitation, helping to strengthen the heart and improve circulation. And, while heart disease remains the leading cause of death in the U.S., running can help lower the risk of future heart problems. The American Heart Association recommends 150-plus minutes of moderate-intensity aerobic activity or 75 minutes of vigorous-intensity aerobic activity (like running) each week to improve cardiorespiratory health.

So you’re already reducing the risk of a cardiac event just by being a runner, but why stop there when you can optimize your heart to become even stronger and healthier? Not every cardiovascular event can be prevented—genetics, sudden triggers, and sometimes simple chance all play a role—but there’s still a lot you can do to keep your heart fit and give it the best possible care so you can enjoy running for as long as you want to run.

🫀 WHY YOU’RE SAFER THAN EVER ON RACE DAY

In a 2010 update to its emergency response guidelines, the American Heart Association put an emphasis on immediate, high-quality chest compressions when performing CPR to minimize delays in restoring bloodflow to the brain and heart.

At the same time, as participation in long-distance races like marathons and half marathons surged, race organizers began expanding cardiac safety measures, including wider access to automated external defibrillators.

A 2025 study published in the Journal of the American Medical Association found that while the incidence of cardiac arrest during long-distance races remained steady between 2000 and 2023, mortality dropped by nearly 50 percent. Researchers attributed the improvement largely to “faster emergency response, particularly quicker access to defibrillation.”

The human heart is a fist-sized organ that accounts for roughly 0.5 percent of your bodyweight. Despite its relatively small size, it is the hardest-working muscle in your body, beating more than 100,000 times a day (typically faster in women than in men). It’s an involuntary muscle, operating without your conscious control or thought, contracting in response to its own electrical impulses. And it’s the only muscle in your body that works all the time and doesn’t get tired, because it’s made up of special cells (called cardiomyocytes) that resist fatigue.

Your heart is a powerful pump that keeps blood moving throughout your body. With each beat, it sends oxygen and nutrients to your cells while carrying away waste, like carbon dioxide. At the same time, it helps maintain healthy blood pressure and—working with your blood vessels—adjusts how fast and where blood flows based on your body’s needs.

Once you start running, your circulation shifts within seconds, and your sympathetic nervous system triggers the fight-or-flight response, usually related to stress, danger, or intense physical activity—when the brain signals the release of hormones like adrenaline. Your circulation and musculoskeletal systems work together to send oxygen-rich blood to your muscles. “All it’s thinking is, how do we get oxygen where it needs to go as fast [as possible],” says Tamanna Singh, MD, director of the Sports Cardiology Center at Cleveland Clinic.

“There’s this period of adjustment from rest to stress,” she says. “When you first start running, it takes a minute or two to get into the flow, and that’s the recruitment process.” Your heart pumps faster and contracts more forcefully with each beat to eject more blood to oxygen-hungry muscles, while also removing heat and metabolic byproducts. Between beats, it relaxes more quickly. While skeletal muscles and the skin see an increase in bloodflow, nonessential body organs, like the kidneys or the stomach, experience a decrease (one reason why eating right before a run can cause GI distress, as digestion is impaired). Once your body gets used to the sudden change, it transitions to a “steady state” or equilibrium.

That’s during a single run. In the long term, consistent running can lead to actual structural changes to the heart. The same way skeletal muscles grow over time when we lift weights, the heart muscle grows when we require it to keep pumping blood faster to support the higher oxygen and energy demands of the exercising muscles (which leads to an increase in VO₂ max, the maximum rate of oxygen your body can use during exercise). Consistent running can also lower your blood pressure—in response to your muscles requiring more oxygen and bloodflow, your body allows vessels to widen to meet the demand. As the heart muscle grows stronger and more efficient, your resting heart rate decreases.

If you use a wearable watch or fitness device, it continuously collects and analyzes your personal health data, providing access to more metrics than you might ever need. When it comes to your heart, here are the stats you should focus on and how much you can train your heart to improve them.

Max Heart Rate

What to Know

The highest number of beats per minute your heart can reach during an all-out effort. It informs your heart-rate training zones, which guide how tempo, threshold, and hard/easy runs should feel.

How to Measure

Common formulas are not one-size-fits-all. The most precise test is done in a lab. A DIY option: Do a 30-minute progression run at threshold, then average your heart rate over the last 10–15 minutes.

How to Train

Largely determined by age and genetics, so you can’t meaningfully raise it. Instead, focus on improving efficiency by training your heart to pump more blood per beat.

Heart-Rate Variation

What to Know

The time between heartbeats in milliseconds. This reflects how well your body balances stress and recovery. Average range: 19–75. Higher numbers signal better recovery; lower can indicate fatigue, stress, or poor sleep.

How to Measure

Requires precise sensors, typically found in a lab. But a wearable can help establish your personal baseline. Track it regularly and focus on trends rather than a single reading.

How to Train

Partly genetic, but lifestyle plays a major role. Prioritize sleep, manage stress, stay hydrated, and allow adequate recovery between workouts.

Resting Heart Rate

What to Know

The number of times the heart beats per minute at rest. It’s a basic marker of cardiovascular fitness. For most adults, it falls between 60 and 100 bpm, though it’s often lower in runners.

How to Measure

Check your pulse for 60 seconds, preferably in the morning. Stress, dehydration, poor sleep, caffeine, and other factors can increase RHR, so watch trends rather than a single reading.

How to Train

Regular running lowers RHR by strengthening the heart so it pumps more blood per beat. Support that adaptation with good sleep, hydration, stress management, and balanced nutrition.

YOUR SMARTWATCH IS NOT A DOCTOR!

The wealth of data accessible via wearable tech can be useful. But as one manufacturer, Garmin, notes, its “watches are not medical devices, and the data provided by them is not intended to be utilized for medical purposes and is not intended to diagnose, treat, cure, or prevent any disease.” You can protect your heart and improve your fitness with tried-and-true methods such as rate of perceived exertion (RPE), a subjective 1–10 scale of how a workout feels.

As an athlete, you already know carbs are your friend, that replenishing with protein after exercise is essential for muscle growth—and that a balanced diet powers your ability to run.

When it comes to your heart, the advice is pretty similar. “Eating whole and more natural [food] is the way to go,” says Jessica Smith, registered dietitian, licensed dietitian nutritionist, and personal trainer based in Easton, Pennsylvania. On the other end of the spectrum are nutrients you should try to avoid, such as saturated fats: They raise low-density lipoproteins (LDL, “bad” cholesterol), which build up in arteries and increase the risk of developing cardiovascular disease. Ultimately, any food is okay in moderation, Smith says. “There’s [no] one food you shouldn’t eat,” she says. What remains true is that some foods are especially good for a runner’s heart. Here’s your guide.

Heart-Healthy Superfoods for Runners

Salmon

Provides protein for muscle repair and omega-3 fatty acids that support heart health and may help reduce inflammation.

Sweet Potatoes

A complex carb rich in fiber and potassium, which delivers steady energy and supports healthy blood pressure.

Bananas

A convenient source of carbohydrates for energy, as well as potassium, which supports heart rhythm and muscle function and prevents cramps.

Oatmeal

A complex carbohydrate that fuels longer runs and contains soluble fiber (beta-glucan), which can help lower LDL cholesterol.

Berries

Packed with antioxidants and polyphenols that support blood vessel health and may help reduce postexercise inflammation.

Nuts (almonds, walnuts)

Provide healthy unsaturated fats, fiber, and magnesium that can help improve cholesterol levels and provide lasting energy.

Food Myths That Should Be DQ’D

—Additional reporting by Pam Moore

Extreme temperatures force your cardiovascular system to work harder, so protecting yourself from the elements can help reduce cardiac strain.

🥶 WINTER

Cold temperatures cause blood vessels to constrict, which can raise blood pressure and make the heart work harder to circulate blood.

→ Do This: Dress in insulating layers to keep your core warm. A vest or thermal layer over your torso can help retain heat, and a hat prevents heat loss from the head.

🥵 SUMMER

Heat forces the heart to pump faster to circulate blood to the skin so the body can cool itself. Dehydration can increase strain on your cardiovascular system.

→ Do This: Wear light-colored, breathable clothing and a hat to limit sun exposure. Use sunscreen and hydrate before, during, and after a run—ideally with electrolytes during longer workouts.

That looming deadline at work that keeps you up at night may feel minor in the grand scheme of things, but add your parent’s upcoming surgery and your children’s busy schedules, and stress quickly builds.

Stress is a natural human reaction that can be positive, keeping you alert, motivated, and ready to avoid danger. But without periods of relief, it can accumulate and turn chronic, flooding your body with high levels of cortisol and adrenaline—triggering inflammation and increasing your heart rate and blood pressure.

By running, you’re already practicing one of the best lifestyle habits for managing stress. At first glance—somewhat ironically—running acts as a stressor itself, triggering a temporary release of cortisol. But that short-term surge serves a purpose: It helps your body adapt, making you better equipped to handle future stress. Over time, running becomes a potent antidote to stress, lowering baseline cortisol and adrenaline levels while boosting endorphins—natural mood elevators and painkillers.

“It’s helpful to consider factors that we can control and improve: Embrace social interaction, build a community of trust, recognize risk factors, and incorporate wellness and mindfulness practices,” says Cleveland Clinic’s Tamanna Singh, MD.

In fact, one of the most powerful tools for de-stressing is practicing mindfulness, says Emily Saul, MS, a licensed mental health counselor in Boston who works with athletes. That can be done through breathing exercises, meditation, or visualization.

Some stress relievers work in minutes, while others build resilience over time. The most effective routines combine quick resets—like breathwork—with longer-term habits like sleep and regular social connection.

Use our matrix to plan your stress-reduction strategy:

Geneva Humdy started running in her early 20s to stay fit and never really stopped. By her 30s she was logging about 20 miles a week, though occasionally after long runs she’d wake up in the middle of the night with her heart racing, gasping for air. The cardiologists she saw couldn’t find anything wrong.

Years later, while hiking in Costa Rica at age 66, Humdy felt something similar—but worse. On the way down the trail, she suddenly struggled to breathe and sensed her heart beating irregularly. When she checked her blood pressure that evening, the reading was dangerously high.

Back in the United States, doctors finally identified the cause: a congenital heart defect that had gone undetected for decades. Humdy underwent two ablation procedures to correct the abnormal electrical signals in her heart.

With her cardiologist’s guidance, she slowly built her mileage back. In 2024, she celebrated her 70th birthday by completing the Ku‘ikahi Half Marathon in Hawaii.

Her experience underscores an important message cardiologists emphasize: Unexplained symptoms shouldn’t be ignored, and finding the right specialist can make all the difference in safely returning to running.

When to See a Cardiologist

• You have a genetic or family history of issues. A cardiologist can assess your risk of having a heart event.
• You’re symptomatic or have noticed even a subtle decline in your performance you can’t explain with nutrition, hydration, electrolytes, overtraining, or undertraining.
• You have cardiac disease and want exercise recommendations and/or a second opinion.
• You’re worried about your heart. “You’re jacking up your sympathetic nervous system, and your heart rate is going to go up—so it’s better to get things checked out,” Singh says.

Pavlína Černá

Senior Features Editor

Pavlína Černá, an RRCA-certified run coach and cycling enthusiast, has been with Runner’s World, Bicycling, and Popular Mechanics since August 2021. When she doesn’t edit, she writes; when she doesn’t write, she reads or translates. In whatever time she has left, you can find her outside running, riding, or roller-skating to the beat of one of the many audiobooks on her TBL list.