Smart devices and wearables are increasingly popular but not many of us are taking full advantage of the insights they provide. A key indicator for health is heart rate variability.

About the Writer

Larisa Dina is a researcher finishing her PhD at King’s College London, who is writing exclusively for the Purposeful Group companies. For over 6 years, her focus has been on digital health, including evaluating the Drink Less app for reducing harmful alcohol consumption and leveraging the Brain Explorer app to understand how people make decisions in their daily lives. Since 2023, Larisa has been on a mission to help increase access to therapy and improve clinical outcomes through the use of AI.

What Your Smartwatch Knows About Your Health (That You Might Not)

In finance, data is power. Continuous tracking, trend analysis, and risk mitigation drive smarter decisions. Now, imagine applying that same mindset to your most valuable asset: your health.

Thanks to wearable technology – think smartwatches, fitness trackers, and health rings – you can now monitor a stream of physiological data 24/7: heart rate, sleep, temperature, or oxygen levels. But among these, one metric has received a lot of attention in recent years in the scientific community for its predictive power and insight: Heart Rate Variability (HRV).

HRV: The Hidden Indicator of Health

HRV doesn’t measure how fast your heart beats, but rather how much time variation there is between heartbeats. For instance, if your heart rate is 60 beats per minute, the gap between each beat is not precisely one second – it fluctuates slightly (e.g., 0.9 s, 1.12 s), and that’s actually a good thing!

This variability reflects the health of your autonomic nervous system (the other important branch of our nervous system besides the central nervous system), responsible for our body’s response to stress and recovery. In turn, the autonomic nervous system consists of two branches:

• The sympathetic branch – sympathetic (“fight or flight”) activity speeds up your heart.
• The parasympathetic branch – parasympathetic (“rest and recover”) activity slows it down.

The better these branches work together, the higher your HRV, and therefore the more adaptable and resilient your body is. In a nutshell, high(er) HRV suggests you are well-rested, balanced, and ready to take on challenges. Low(er) HRV can signal fatigue, stress, poor sleep, dehydration, or even early signs of illness. Notice the relative wording (i.e., higher rather than high). This is because monitoring these insights should be relative to you; for example, if you’re making an effort to improve your sleep hygiene, you might notice your HRV this month is higher than in the months prior.

Think in Trends, Not Snapshots

Just as you wouldn’t judge a portfolio based on one day’s movement, you shouldn’t worry about a single HRV reading. Instead, look at your personal trends. Is your HRV dipping consistently over a few days? That might be a sign that your body needs recovery. Thinking

in relative terms again, what recovery means to you could be different than what it means to other people – e.g., being more consistent in the gym, going to bed at a consistent and reasonable time every night, managing stress etc. This is where other metrics tracked by your wearable could come in handy.

With consistent tracking, HRV becomes a powerful feedback loop for optimising performance and preventing burnout.

Can You Trust the Data?

Good news: wearable HRV tracking is getting more accurate. Devices like WHOOP, Oura, and Apple Watch now capture HRV data during sleep. This is because readings are more reliable when your body is at rest and there are less extraneous or uncontrolled factors in your environment.

In fact, some studies show wearables match lab-grade electrocardiograms (ECGs; tests that record the electrical activity of the heart, such as heart rate and rhythm) for long-term HRV trends. While very short-term HRV measures can still be hit-or-miss, especially in individuals with heart conditions, tracking broader, lower-frequency HRV markers remain useful for most people.

Smarter Monitoring, Smarter Living

For busy professionals, HRV offers something rare: a simple number that reflects how well you’re doing, even before symptoms appear. Use it to guide when to push, when to recover, and when to investigate further.

Think of it as the volatility index for your health. And like any great dashboard, it becomes more powerful over time.

So next time you read the health report on your smartwatch or wearable device of choice, don’t just check steps or calories. Take a moment to check your HRV. It is a powerful index in your health portfolio.