Tracking how often your heart beats per minute can tell you a lot about your health. It starts with your heart rate.
“This is the number of times your heart beats per minute,” says Dr Jonathan Lyne, a cardiology consultant at the Blackrock Clinic, the Beacon Hospital and St Vincent’s in Dublin.
“It varies throughout the day, beating faster when we exert ourselves or experience stress and slower when we are at rest.”
It’s easily measured: all you do is use your first and middle fingers to feel for the pulse on the inside of your wrist or side of your neck and count how many times it throbs in the space of 60 seconds. That’s your resting heart rate, provided you’re sitting comfortably.
“For adults, it normally ranges from 60 to 100 beats per minute [bpm],” says Lyne.
Should you worry if it’s higher or lower? Not if you’re elderly and it’s slightly elevated.
“Generally, our heart rate increases with age as the muscles pump blood less efficiently,” he says.
If you’re exceptionally fit and have a low resting heart rate, that’s not necessarily cause for concern.
“Athletes can have resting heart rates as low as 35bpm,” he says.
Dr Cailbhe Doherty, physiotherapist and assistant professor at the UCD School of Public Health, Physiotherapy and Sports Science, warns that there are circumstances when a lower or higher heart rate can signal problems.
“A consistently high resting heart rate may indicate stress, dehydration, or underlying issues such as cardiovascular disease, hyperthyroidism, or infection. “A low resting heart rate can be a sign of a heart block or hypothyroidism.
Lyne adds that medication and issues with the heart’s electrical system can also affect heart rate.
“As a cardiologist, I judge whether a patient’s heart rate is appropriate for them based on their individual context,” he says. “A fit young person presenting with a heart rate of 38 is completely different to an 80-year-old with the same heart rate.”
Finger on the pulse
Our understanding that heart rate is connected to health dates back at least to the time of Herophilus of Alexandria, who lived between 325 and 255 BC. Known as the father of anatomy, he is said to have devised a clock to time the pulse.
Since then, we have developed more precise tools to measure heart rate.
“The electrocardiogram is one,” says Lyne. “It records the heart’s electrical activity to measure the heart rate.”
We have also learned what affects the heart rate.
“High blood pressure, for example, can push the heart to beat faster to manage its increased workload,” says Doherty. “Caffeine and alcohol can increase the heart rate. The nicotine in cigarettes causes it to rise. And emotional states such as stress, excitement and anxiety can trigger an increase in heart rate too.”
Giles Warrington, professor of human performance and innovation at the University of Limerick, describes how exercise benefits your heart by lowering your resting heart rate.
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It’s all to do with stroke volume or the amount of blood squeezed from the heart’s left ventricle per beat.
“Athletes have a lower resting heart rate because they have a higher stroke volume,” says Warrington. “Their heart pumps more blood per beat.”
You can train your heart to do this, too.
“The heart responds to aerobic exercise by pumping more blood to the muscles,” says Warrington. “Initially, it will have to beat faster to circulate that increased volume of blood. But over time, its stroke volume will increase. That’s what makes exercise feel easier and it’s also what reduces your resting heart rate.”
Heart rate variability
Your heart rate is just one measurement that can tell you something about your health. Your heart rate variability (HRV) is another.
“Your heart isn’t a metronome,” says Doherty. “There are fluctuations in timing between each heartbeat. That variability gives the heart flexibility to respond rapidly to a changing environment of different stressors.”
Your HRV is determined by the activity of your autonomic nervous system, which controls stress response.
“That system maintains your body in a state of balance called homeostasis by controlling how your heart rate and other body processes react to the stressors you face,” says Doherty. “It has two branches: the sympathetic, or fight or flight mode, which urges your heart to speed up; and the parasympathetic, or rest and digest mode, which urges it to slow down.”
That system is in constant flux throughout the day, which means your heart rate is, too. Your HRV measures just how much it varies and in a healthy adult, that’s normally between 20 and 200 milliseconds.
There will be times when your HRV is high and other times when it’s low. What matters most is how it trends over time. According to Lyne, someone whose HRV is generally high is someone whose body is effectively managing stress.
“A higher HRV usually indicates a heart that’s capable of responding appropriately to the body’s changing needs,” he says.
A lower HRV could indicate the body is under stress.
“That stress could be activating the sympathetic system, keeping the heart rate high and reducing its variability,” says Lyne.
Tracking your stats
Until relatively recently, most people rarely measured their heart rate or HRV. But thanks to the introduction of smartwatches and fitness trackers, a growing number of people are now keeping constant track of both.
Dr Mary Coghlan, a medical doctor and partner at EY Ireland, where she leads health data and analytics, welcomes this development.
“The fact that we can monitor this data ourselves on a day-to-day basis gives us a greater awareness of our health and can empower us to take action to maintain and improve it.”
This data can enhance our motivation levels.
“When you see that your new exercise routine is reducing your resting heart rate, you’ll be more inclined to keep it up,” says Coghlan.
It also makes clear the damage done by poor lifestyle habits.
“For example, if you overindulge in alcohol, you’ll see that in your higher heart rate the next day,” she says. “That might make you think again next time.”
Tracking your HRV can be equally insightful.
“If it’s out of sync, it can be an early sign that you’re getting sick, that you’re not getting enough sleep or are stressed,” she says. “You’re likely to know yourself what the cause is and can take action to do something.”
Fitness enthusiasts often use their heart rate and HRV to gauge how well they are responding to their training. “Your HRV should normalise quickly after exercise but if it falls, that can mean your body is fatigued or not coping well with stress, which could be a cue to ease off on training until it’s recovered,” says Warrington.
Interpreting how our ticker tocks can also help us stay in good health, and a fitness tracker can prompt us to embrace healthier habits. However, Warrington says that such things aren’t vital.
“If they encourage people to become more active, that’s a good thing,” he says. “But lots of us are already in tune with our bodies. We know when they don’t feel right and can tell when we should or shouldn’t put them under additional stress. We’ve become a tech-aware society, and there’s no harm in using wearable technology to increase our awareness of our health status, but we don’t need them to stay healthy.”
Push exercise intensity to point where you can ‘just about’ maintain a conversation
The HSE advises people aged over 18 to practice moderate intensity activity for at least 30 minutes a day, five days a week.
“You should just about be able to maintain a conversation when exercising at this intensity,” says Prof Giles Warrington.
If you measure your heart rate, you can also use that to gauge how hard you’re working. Warrington advises aiming for 65% to 75% of your estimated maximum heart rate if you want to exercise at moderate intensity.
“There’s a formula to determine your maximum heart rate,” he says. “It’s 220 minus your age, plus or minus 10,” he says.
“There’s some variability in there.” Dr Cailbhe Doherty recommends specific forms of exercise for those who want to strengthen their heart and ensure it pumps more efficiently. “Aerobic exercise such as brisk walking, running, swimming and cycling lower the resting heart rate over time,” he says.
Strength training and high-intensity interval training can further enhance the benefits.
“High-intensity interval training can improve cardiovascular fitness rapidly, potentially leading to more significant reductions in resting heart rate,” says Doherty.
He urges those who track their heart rate and HRV to adjust their training based on these readings.
“Your HRV and heart rate can be used as indicators of physiological readiness,” he says. “High HRV and low heart rate suggest readiness for intense workouts while low HRV and high heart rate call for recovery.” You should pay attention to other wellness indicators too. These include muscle soreness, fatigue levels and overall mood.
Recovery should also be prioritised. It will have a beneficial impact on heart rate and HRV and consequently lead to better performance and overall health.
Doherty’s final tip is to take any sudden unexplained changes in heart rate or HRV seriously. “If they don’t align with recent training or stress levels, they warrant closer attention,” he says.
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