What is heart rate variability? What your HRV says about your health

The heart is one of the hardest-working muscles in your body, and your heart rate is one of the most widely used measures of cardiovascular health. But there’s another powerful data point that’s becoming more and more mainstream, and increasingly telling of your wellbeing and longevity: heart rate variability, or HRV.

Here’s what you need to know about it.

What is heart rate variability (HRV)?

Before understanding how heart rate variability works, it’s helpful to know exactly how your heart rate works. 

Put simply, your heart rate is how fast your heart is beating at any given moment, measured as the number of beats per minute. It might seem steady, but it actually fluctuates depending on your activity. If you’re in a resting state – say you’re sitting at your desk or relaxing on the couch – your heart rate is typically lower, while if you’re moving around – perhaps doing intense exercise – it’s generally higher.

Your heart rate variability is the difference in time between each of those beats. Even if your heart rate looks stable – say, 70 beats per minute – the exact timing between beats isn’t perfectly even. Those small variations reveal how well your body is balancing stress and recovery. 

For the most part, a higher HRV is considered more favourable – it shows that your cardiovascular system is more adaptable and your body is able to switch between effort and rest more efficiently. A lower HRV can indicate that you’re stressed, tired, ill or run-down. Your HRV can also change over time, indicating improved fitness.

Is HRV unique to you?

Yes, your heart rate variability is entirely unique. A high HRV for one person may be a low one for someone else, which is why it’s best not to compare your number to others. Instead, you should focus on your baseline and track changes to your own readings.

What affects heart rate variability?

At its core, heart rate variability is driven by your autonomic nervous system – specifically the balance between your sympathetic “fight or flight’’ response and your parasympathetic “rest and digest’’ response. When your body is calm, recovered and feeling safe, the parasympathetic nervous system is more active, leading to higher HRV. When you’re stressed, overwhelmed, sick or running on little sleep, the sympathetic nervous system takes over, which typically lowers HRV.

However, there are many other factors that can change your reading.

Factors you can’t control

• Genetics: Your baseline HRV is heavily determined by your genetic makeup
• Age: HRV typically gets lower as you age
• Circadian rhythm: Your HRV can also change across the day, getting higher at night and lower in the morning
• Hormones: Where you are in your menstrual cycle can impact your HRV
• Environment: While there are certainly aspects of your environment you can control, things like outside temperature, air quality, humidity and altitude can influence your HRV
• Illness: Both seasonal illnesses and chronic conditions can affect HRV, as can the medications you take to treat them

Factors you can control

• Diet: What you eat massively influences your HRV, with a diet rich in nutritious foods generally associated with a higher HRV
• Exercise: The more you move your body, the higher your HRV typically is
• Emotional state: Stress and changes in mood can contribute to a lower HRV
• Sleep: If you’re lacking in sleep, your HRV may be lower
• Alcohol and smoking: Using alcohol and tobacco can decrease your HRV

Because HRV responds quickly to lifestyle changes, it's often used in biohacking to test how habits can affect the body in real time.

How to check or monitor your heart rate variability

There are several ways to assess your heart rate variability, either with a doctor or yourself, using a wearable device.

Your doctor will usually use a test known as an electrocardiogram (EKG), which records your heart’s electrical activity. It’s typically used to diagnose heart conditions by measuring your heart’s rate and rhythm, but it can also gauge your HRV by tracking beat-to-beat intervals.

At home, many wrist-worn fitness devices have the capability to measure HRV, too. While often not as accurate as an EKG, you can get a general idea of patterns and trends.

What is a good heart rate variability?

As we know, heart rate variability varies from person to person. It’s influenced by a range of factors and can change depending on your activity levels and even the time of day.

Generally speaking, though, HRVs sit in the following ranges:

• Low heart rate variability: Less than 19 milliseconds
• Normal heart rate variability: 19-75 milliseconds[1]
• High heart rate variability: More than 75 milliseconds

Your best bet is to figure out your HRV baseline, then compare any increases or decreases to that number. Your healthcare provider can help you figure out your baseline.

Can you improve your HRV?

While it’s not a guarantee that your heart rate variability will improve, there are many habits you can change to try to boost it. These include:

• Eat a healthy diet: Focus on nutritious foods like whole grains, fruits, vegetables, lean meats, nuts, seeds and healthy fats. These are all good for your heart, especially monounsaturated fats from extra-virgin olive oil, nuts and avocado. Try to steer clear of saturated fats, ultra-processed foods, refined carbohydrates, and foods high in sugar and salt
• Doing regular exercise: Engaging in regular physical activity can increase your HRV. Try to incorporate at least 150 minutes of moderate-intensity cardiovascular exercise per week into your routine, such as swimming, cycling or brisk walking. Ensure you get adequate rest in between, too. Rest days allow your heart to recover
• Staying hydrated: Aim for 2.1 litres (8 cups) of water per day, which is the amount recommended for adult women [2]
• Managing stress: Stress can negatively impact HRV, so actively managing it can make a difference. Try calming activities like yoga, journaling, meditation and deep breathing
• Prioritising mental health: Beyond day-to-day stress management, looking after your mental health can support both your HRV and overall wellbeing. Many of the stress management techniques above can help, as can therapy, counselling and mindfulness practices
• Getting enough sleep: Aim for 7-9 hours of sleep each night and implement a few healthy habits to improve your sleep quality. These include blocking out screens for about an hour before bedtime; avoiding caffeine, heavy meals and alcohol, especially later in the day; going to bed and waking up at the same time each day; and making your bedroom a cool, dark and quiet environment
• Avoid alcohol and smoking: Try to stick to the recommended alcohol intake of no more than 10 standard drinks each week [3], and ideally have a few days each week where you abstain completely. Quitting smoking is always best, but even cutting back may help to improve your HRV 

Is it normal for HRV to fluctuate?

Yes, it’s completely normal for heart rate variability to fluctuate over time, each day and even within a single day. There are so many variable factors that influence it, and these can shift rapidly. 

Rather than focusing on moment-to-moment fluctuations, you want to look for overall trends in your HRV. Figure out your baseline, then compare it to an average HRV over time. 

What is HRV training?

Heart rate variability training is a type of training plan that relies on HRV to guide your workouts. You adjust the type and intensity of the training you do based on your reading that day, with the goal of balancing effort and recovery. It can improve performance, prevent injury or overextending your body, and allow it to adequately rest.

You start by measuring your HRV, usually in the morning, then comparing it to your baseline. If your HRV is on the lower end that day, it can indicate that your body is under strain. You might then engage in a light yoga session or even a complete rest day. If your HRV is higher, it can mean your body is ready to engage in a more strenuous workout.

When to worry about your heart rate variability

A few scenarios could indicate that heart rate variability is linked to something more serious. Reach out to your doctor if any of the following apply:

• Abnormally low HRV: Low HRV doesn’t automatically mean something is wrong, but it can be an early signal that your body is under more strain than usual. If the pattern continues over days or weeks, it’s worth checking in with a healthcare professional to rule out underlying conditions and assess what might be contributing. A low HRV is often tied to issues such as chronic stress, exhaustion and inflammation, as well as more severe health conditions.
• Abnormally high HRV: Even though a high HRV is associated with better health, a very high or erratic HRV could indicate heart issues such as an arrhythmia (irregular heartbeat). It’s crucial that you see your doctor, especially if you’re noticing associated symptoms like dizziness, shortness of breath, palpitations and chest pain

And remember, while HRV is a useful indicator, it doesn’t give the complete picture. Using it alongside other measures can give you a more accurate and comprehensive idea of your overall health.

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