Nancy Wells crossed the finish line of the 2025 Mercy Health Glass City Half Marathon, in Ohio, feeling elated. The now 55-year-old has run over 60 marathons and half marathons and, at 2:41:26, this was her slowest-ever half – but finishing it was special, because it’s the race during which she had suffered a heart attack a year earlier.
On race morning in 2024, something felt wrong. Wells blamed the muggy weather and eased into the race more than usual. But it took all her energy to get through the first two miles. Then she felt a weird chest pressure. She slowed to a walk, then called her husband to tell him that she wasn’t feeling well. The last thing that she remembers is making a turn at about four miles. She woke up in hospital with a tube down her throat to be told that 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 hospital, a procedure to place an artery stent – a flexible tube that helps to open a narrowed vessel and increase blood flow – and a supervised programme of cardiovascular rehabilitation. Once her heart’s ability to pump blood had improved to a 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 is the second leading cause of death in the UK, and the leading cause in British men, running can help to lower the risk of future heart problems.
The NHS recommends 150-plus minutes of moderate-intensity aerobic activity or 75 minutes of vigorous-intensity aerobic activity, such as 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 optimise 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 that you can do to keep your heart fit and give it the best possible care, so that you can enjoy running for as long as you want to.
Your heart on running
Your heart is a fist-sized organ that accounts for roughly 0.5% of your body weight. It’s the hardest working muscle in your body, beating more than 100,000 times – typically faster in women than men. It’s an involuntary muscle, which means that it operates without your conscious control and contracts in response to its own electrical impulses. And it’s the only muscle in your body that works all the time without tiring, as it’s made up of special cells – cardiomyocytes – that resist fatigue.
With each beat, your heart sends oxygen and nutrients to your cells while carrying away waste. It helps to maintain healthy blood pressure and, working together with your blood vessels, adjusts how fast and where your 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, releasing hormones such as 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, director of the Sports Cardiology Center at Cleveland Clinic.
‘There’s a period of adjustment from rest to stress,’ she says. ‘When you start running, it takes a minute or two to get into the flow – that’s the recruitment process.’ Your heart pumps faster and contracts more forcefully to send more blood to oxygen-hungry muscles, while also removing heat and metabolic by-products. Skeletal muscles and the skin see an increase in blood flow, while non-essential body organs, such as the kidneys or the stomach, experience a decrease. Once your body adjusts, it transitions to a ‘steady state’.
That’s during a single run. In the long term, running brings structural changes to the heart. Just as skeletal muscles grow when we lift weights, the heart grows when we require it to pump blood faster to support the demands of exercising muscles. Consistent running can also lower your blood pressure – in response to your muscles needing more oxygen and blood flow, your body allows vessels to widen. As the heart grows more efficient, your resting heart rate decreases.
4 important health metrics to measure
Your fitness tracker – if you wear one – analyses your health data, providing you with a bounty of metrics. Here are the four key statistics to focus on, how to measure them without a wearable or lab test and how you can train your heart to improve them.
What is it?
The highest number of beats per minute that your heart can reach during an all-out effort.
How do you measure it?
Do a 30-minute run at threshold pace, then average your heart rate over the last 10 to 15 minutes.
How can you train it?
Focus on improving efficiency by training your heart to pump more blood per beat.
What is it?
The time between beats in milliseconds. It reflects how well your body balances stress and recovery.
How do you measure it?
A wearable can establish your baseline. Track it regularly and focus on trends rather than a single reading.
How can you train it?
Manage stress, prioritise your sleep, stay hydrated and allow recovery between your workouts.
What is it?
The number of heart beats per minute at rest. It’s a basic marker of cardiovascular fitness.
How do you measure it?
Count your pulse for 60 seconds. Stress, poor sleep, caffeine and other factors increase RHR.
How can you train it?
Running regularly will lower RHR by strengthening the heart, so that it pumps more blood per beat.
What is it?
The maximum amount of oxygen that your body can use during exercise. It reflects cardio efficiency.
How do you measure it?
Try the Cooper Test: run as far as you can in 12 minutes, then use 35.97 x your distance (in miles) minus 11.29.
How can you train it?
Improve with high-intensity exercise such as interval runs and HIIT sessions with strength moves.
Your smartwatch is not a doctor
The wealth of data from wearable tech can be useful, but as Garmin notes, its ‘watches are not medical devices and the data provided by them is not intended to be utilised for medical purposes or to diagnose, treat, cure and prevent any disease’. You can protect your heart and improve your fitness with tried-and-true methods such as rate of perceived exertion (RPE), which is measures how a workout feels on a subjective scale of one to 10.
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