Have you ever checked your smartwatch or fitness tracker and noticed your heart rate variability (HRV) has dropped? Perhaps you've been monitoring this number for a while and can't quite make sense of why it changes or how to improve it. You're not alone.

Many of us track our health metrics diligently, but understanding what they mean—and more importantly, what actions to take—can feel overwhelming. Today, we're demystifying HRV: what it is, why it fluctuates, and how you should incorporate it into your life. 

What is Heart Rate Variability and the Autonomic Nervous System?

Simply put, HRV measures the variation in time between each heartbeat. It is reflective of your body’s autonomic nervous system - the part of your nervous system that works without conscious effort. There is the ‘rest and digest’ mode that activates when your body is calm, slowing down functions like heart rate to allow you to relax. This is contrasted against the ‘fight or flight’ mode that kicks in during stressful situations to keep you alert and prepared, raising your heart rate.

One key physiological process that influences HRV is respiratory sinus arrhythmia (RSA), which refers to the variation in heart rate that occurs during a breathing cycle. As you breathe in, your heart rate slightly increases and as you breathe out, your heart rate slightly decreases.

Your HRV is an important data point which can be influenced by many daily habits and choices. Factors that typically improve HRV include regular exercise, good sleep quality, proper hydration, balanced nutrition, and stress management practices like meditation.

While many of us think a perfectly steady heartbeat is ideal, there are some nuances to it. It is correct in the general sense that we do not want a grossly irregular heartbeat. However, when you look closely a healthy heart actually has slight variations between beats. Think of it this way: your heart isn’t a metronome ticking at the exact same pace. It’s more like a responsive drummer, subtly adjusting the tempo based on your body’s changing needs. These subtle variations are good—they show your body can adapt quickly to different situations.

Your Unique Heart Rhythm

Your HRV is as unique as your fingerprint. While lifestyle choices certainly impact your heart's rhythm, genetics also plays a significant role—accounting for anywhere between 13% to 23% of your HRV profile according to research. This means that your baseline HRV is partly determined by your DNA.

Age also creates natural variations in HRV. Younger people typically show different patterns than older adults, and what is considered "good" varies widely across different life stages. This natural diversity means there's no single perfect HRV number that everyone should target.

The key takeaway? Focus on your personal HRV journey rather than comparing yourself to others, work on improving your baseline through healthy habits, firstly by understanding the changes in HRV. 

Why Your Daily HRV Fluctuates

If you're tracking your HRV, you might notice it changes—sometimes dramatically—from one day to the next. This is perfectly normal! Here's why:

Exercise and Physical Activity

One of the most significant factors affecting your daily HRV is exercise. Intense workouts temporarily lower your HRV as your body works hard to recover. This doesn't mean the exercise was bad for you—quite the opposite! This temporary dip is part of the training effect that ultimately strengthens your heart and nervous system.

After a particularly challenging workout, don't be surprised to see your HRV drop the following day. This is your body's way of saying, "I'm working on recovery!" Give yourself time to rest, and you'll likely see your HRV bounce back, often higher than before.

Sleep Quality

Had a poor night's sleep? Your HRV will almost certainly reflect this. Sleep is when your body recharges, and interruptions to this process show up clearly in your HRV measurements.

Even factors like room temperature, light exposure, or having a late meal can impact your sleep quality and, consequently, your HRV. Creating consistent sleep habits can help stabilise your HRV readings over time.

Life Changes and Health Status

Major life events, like moving house, changing jobs, or planning a wedding, can impact your HRV. Even positive changes can create a stress reaction that affects your readings.

Health factors matter too. HRV tends to decrease with age and is generally higher in women compared to men. For women, hormonal fluctuations throughout the menstrual cycle and during pregnancy can cause regular changes in HRV. These are normal adjustments your body makes. Low HRV can also be a key indicator of future health problems, such as diabetes, high blood pressure, and anxiety, signalling reduced resilience and adaptation to stressors.

When you’re fighting an infection (even before you have symptoms), your HRV often drops. This can actually be a useful early warning sign that your body is working harder than usual.

Stress Levels

Your body's stress response has a direct impact on your HRV. When you're stressed—whether from work deadlines, relationship challenges, or even the news—your body releases molecular messengers that decrease HRV temporarily. In situations of chronic stress, your body might constantly be activated in the “fight or flight” mode, leading to a direct reduction in HRV via an overall elevated heart rate or indirectly through reduced quality of sleep. Chronic stress can also release hormones that increase your appetite leading to emotional eating, and also increase your body’s storage of unused nutrients as fat to prepare for upcoming challenges.

This is one reason why practices like meditation and mindfulness can improve HRV in the long run—they help activate your body's relaxation response. A quick way to test this would be to practise deep breathing exercises - 4 seconds in, 6 seconds out, and you will likely see an increase in your HRV. 

Understanding the Autonomic Nervous System (ANS) and HRV

The Autonomic Nervous System (ANS) is like the body’s autopilot, managing essential functions such as heart rate, blood pressure, and digestion without us having to think about it. The ANS has two main branches: the Sympathetic Nervous System (SNS) and the Parasympathetic Nervous System (PNS).

The SNS is your body’s “fight or flight” response. Imagine you’re suddenly faced with a stressful situation, like a near-miss car accident. Your SNS kicks in, increasing your heart rate and blood pressure to prepare you for action. This response is crucial for survival, but if it’s constantly activated, it can lead to issues like high blood pressure and chronic stress.

On the flip side, the PNS is your “rest and digest” mode. After a hearty meal or during a relaxing evening, your PNS helps slow down your heart rate and lower your blood pressure, promoting relaxation and recovery. This balance between the SNS and PNS is vital for maintaining both physical and mental health.

Heart Rate Variability (HRV) measures the interplay between these two systems. Higher HRV indicates a stronger parasympathetic influence, suggesting your body is good at relaxing and recovering. Lower HRV, on the other hand, points to a dominant sympathetic influence, which might mean your body is in a constant state of alertness. Understanding and monitoring your HRV can provide valuable insights into your overall health and well-being.

HRV Metrics and Calculations

This one is for the nerds if you're not one for detail, skip this section.

HRV metrics and calculations are like the tools in a mechanic’s toolbox, helping you understand the intricate workings of your heart and autonomic nervous system activity. Here are some key metrics:

• Root Mean Square of Successive Differences (RMSSD): Think of this as measuring the tiny time differences between each heartbeat. It’s a real-time snapshot of how your heart is responding to the parasympathetic nervous system.

• Standard Deviation of Normal-to-Normal Intervals (SDNN): This metric gives you the average variability in your heartbeats over a period, usually in milliseconds. It’s a broader view of your heart’s rhythm.

• pNN50: This percentage shows how often your heart rate changes significantly from one beat to the next, indicating parasympathetic activity. A higher pNN50 means your body is good at relaxing.

• Low Frequency (LF) and High Frequency (HF) Power: These metrics measure the power of different frequency components of your HRV. LF is often associated with both sympathetic and parasympathetic activity, while HF is linked to parasympathetic activity. The balance between LF and HF can tell you a lot about your autonomic nervous system’s state.

These metrics can reveal a lot about your health. For instance, consistently low HRV can be a red flag for issues like high blood pressure, heart disease, and mental health disorders. Conversely, high HRV is often seen in healthy adults, athletes, and those who engage in regular physical activity, indicating good physical and mental health.

HRV data can also help you understand how your body responds to stress and exercise. For example, a drop in HRV after a tough workout is normal and shows your body is working on recovery. However, if your HRV remains low, it might be a sign of overtraining or burnout.

By keeping an eye on these metrics, you can gain valuable insights into your autonomic nervous system activity and take proactive steps to maintain your health and well-being.

Focus on Trends, Not Daily Numbers

To accurately monitor your heart rate variability, use medically validated devices such as chest straps monitors or wrist worn fitness devices. For consistent baseline readings, measure your resting HRV at the same time daily—ideally first thing in the morning before rising. This resting measurement represents the gold standard for establishing your personal HRV baseline and tracking meaningful changes over time.

Here's perhaps the most important takeaway: don't stress about daily HRV fluctuations. Instead, look at your weekly and monthly averages. Single-day readings are like checking the weather for one hour—interesting, but not the complete picture. Your long-term HRV trend gives you much more valuable information about your overall health trajectory.

Most quality HRV tracking apps will show you these trends over time, making it easier to spot meaningful patterns rather than getting caught up in day-to-day variations.

Practical Ways to Improve Your HRV

Ready to take action? Here are evidence-based strategies to improve your HRV over time:

1. Prioritise Recovery

Though you are encouraged to exercise regularly, it is paramount to give your body adequate time to recover after intense exercise. This might mean incorporating more gentle activities like walking, swimming, or yoga between more challenging workouts.

Listen to your body—if your HRV is significantly lower than usual, consider opting for active recovery to improve heart rate variability rather than pushing through another high-intensity session.

2. Develop Consistent Sleep Habits

Aim for 7-9 hours of quality sleep each night. Try to go to bed and wake up at similar times, even on weekends.

Create a sleep-friendly environment: cool, dark, and quiet. Consider limiting screen time in the hour before bed, as blue light can disrupt your body's natural sleep signals.

3. Manage Stress Effectively

Find stress management techniques that work for you. This could be meditation, deep breathing exercises, spending time in nature, or engaging in hobbies you enjoy. Don’t let the numbers run your life, HRV is individualistic and you should use it as a tool to understand what works for you, rather than comparing against others which becomes an additional stressor. 

Even brief moments of relaxation throughout your day can make a difference to your overall stress levels and HRV. Go on that 15 minute walk during lunch, make time to catch up with friends or do an activity you enjoy in the evenings.

4. Nourish Your Body

A balanced and healthy diet rich in omega-3 fatty acids, B vitamins, and plant compounds may support higher HRV. Consider incorporating more fatty fish, colourful fruits and vegetables, nuts, and seeds into your meals. Cutting down on alcohol and tobacco use, improving your body weight can increase your HRV.

Stay hydrated! Even mild dehydration can impact your HRV readings. 

5. Build Consistency

Perhaps the most powerful approach is consistency. Rather than dramatic lifestyle overhauls, focus on small, sustainable changes you can maintain long-term. At the end of every month, review the changes you have made, understand what works for you and get a feel for how this has impacted the overall trend in your HRV. 

Regular, moderate exercise is generally better for improving HRV than occasional intense workouts followed by prolonged inactivity. A stable HRV even while training hard highlights the ability of your health to respond to the new stressor and renormalise quickly.

The Bottom Line

Your HRV is a window into your body's adaptability and resilience. Rather than a number to worry about, think of it as feedback—information your body is providing to help you make healthier choices.

By understanding the factors that influence HRV and focusing on long-term trends rather than daily fluctuations, you can use this powerful metric to guide your wellness journey. 

Remember, improving your HRV isn't about perfection—it's about progress. Small, consistent steps in the right direction will yield meaningful results over time. Your future self will thank you for the investment you're making today.