Small, moment-to-moment fluctuations in the timing between heartbeats are offering scientists and consumers new insights into how the body manages stress, exercise, and ageing.

These microvariations, known as heart rate variability, are being tracked by a growing number of people using wearable devices that translate complex physiology into simple data.

London-based health tech worker Artem Kirillov learned to use heart rate variability readings to decide when to rest or train. He said that after factoring this score into his workout routine, he felt more “in balance” and even created an app to help others track stress through similar data.

Interest in heart rate variability has risen as wearable technology becomes more widespread and research output grows, according to Deepak Bhatt, director of Mount Sinai Fuster Heart Hospital in New York City. Still, experts caution that the numbers need to be interpreted thoughtfully.

Here's What They're Not Telling You About Your Retirement

Bhatt explained that while the heart should beat regularly, minor variability between beats is both normal and healthy. Extreme irregularity can indicate arrhythmia, which can lead to complications such as stroke or heart failure.

But on a much smaller time scale, measured in milliseconds, high variability usually signals a system that can quickly adapt to stress and relax thereafter.

There is no universal ideal score since the results depend on age, sex, fitness, and device accuracy. One wearable brand reports average variability values of 65 milliseconds for men and 62 for women, with younger users tending to show higher averages. Bhatt emphasizes that interpreting these values should focus on individual trends rather than comparisons.

Heart rate variability works as an indicator of how effectively the nervous system switches between its fight-or-flight and rest-and-digest responses. When the body is under stress or exertion, heart rate steadies and variability drops. Once returned to a calm state, that variability rises again, showing resilience and flexibility.

This Could Be the Most Important Video Gun Owners Watch All Year

Dennis Larsson of Kiel University, whose research focuses on this metric, said that higher variability demonstrates a body capable of adapting to stressful and relaxed environments appropriately. Lower variability can indicate being locked into a stress-dominant state, a common feature of modern life.

Clinicians have found heart rate variability useful in assessing cardiac rhythms and identifying potential warning markers for conditions such as atrial fibrillation. In sports, athletes often use the measure to decide on recovery periods, noting that variability should fall during exertion and rise again as the body restores.

Research also links heart rate variability to mental health. A review from 2023 found reduced variability among people diagnosed with anxiety and depression. Larsson said this pattern can signal a body caught in a sustained state of duress.

Additional studies have connected lower variability to post-traumatic stress disorder, dementia, and schizophrenia, with some evidence that variability improves after psychotherapeutic or neurological treatments.

However, results across studies are mixed. Researchers note that methodologies vary widely, from five-minute measurements to full-day assessments, and accuracy differs across devices. The diversity of approaches makes comparison challenging.

Beyond mental health, variability may provide clues about ageing and inflammation. A review in 2024 proposed that because chronic stress influences inflammation and therefore affects age-related disease, heart rate variability might serve as a proxy for how well the body is coping with cumulative stress.

Some researchers and clinicians believe techniques such as structured breathing may help people intentionally influence heart rate variability. Tim Herzog, a psychologist and biofeedback specialist in Virginia, recommends gentle breathwork sessions—about twenty minutes twice daily—as a simple method to support variability through mindful control of inhale and exhale patterns.

Preliminary studies suggest such breathing practices can lessen symptoms of PTSD and depression and may also aid sleep, blood pressure, and chronic pain. Still, the evidence remains early, and experts emphasize the need for larger controlled trials to determine whether deliberate training is beneficial or merely coincidental.

Larsson views heart rate variability primarily as an observation tool rather than something to manipulate directly.

Bhatt likewise notes that variability usually rises when other healthy behaviors improve, such as exercise and adequate sleep, but it remains unclear whether the variability itself drives the benefit or simply mirrors broader wellness.

Accuracy remains a key consideration, said Karin Steere of the University of Puget Sound, whose research shows chest-worn devices outperform wrist models. She cautions users to focus on long-term trends, since variability fluctuates naturally throughout the day.

Steere advises observing patterns over time and linking them to lifestyle factors such as sleep quality or alcohol intake. Repeated daily readings, she said, can help individuals see how their bodies respond to habits and changes.

Herzog agrees that step-by-step tracking can strengthen awareness rather than replace other health assessments. In his view, the value comes from noticing how physiological data relate to personal experience.

Bhatt adds a note of perspective. For most people, simpler markers like heart rate, blood pressure, weight, waist size, and cholesterol offer more straightforward insight into health. “Every adult should know those numbers,” he said, underscoring that heart rate variability, though fascinating, is only one part of a much bigger picture.

---

Are you feeling overwhelmed or hopeless right now? Have you been withdrawing from people or activities you usually enjoy? Are you having thoughts about hurting yourself, or feeling like things will never improve?

You do not have to handle those feelings alone. Support is available, and talking to someone can make a difference. You can reach out to the 988 Suicide & Crisis Lifeline by calling or texting 988, or by chatting online at 988lifeline.org. Trained counselors are available 24 hours a day to listen and help.

If you believe someone is in immediate danger, call emergency services right away. Even a small step, like reaching out to a trusted friend, family member, or professional, can help create a path forward.