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Heart rate variability: A window into mental and physical health
Subtle variations in the intervals between heartbeats are gaining attention as a powerful metric for assessing stress, fitness, and even biological ageing. Researchers and health enthusiasts alike are turning to this nuanced measurement to fine-tune wellness strategies.
The personal journey behind the data
Artem Kirillov, a 40-year-old London-based health tech professional, once believed relentless gym sessions were the key to progress. "I preferred pushing myself, even when I felt unwell," he admits. That mindset shifted when he began monitoring his heart rate variability (HRV)-a metric his smartwatch tracked alongside basic heart rate.
Unlike a simple heart rate count, HRV measures the millisecond-scale fluctuations between consecutive heartbeats. Kirillov soon noticed how his HRV scores influenced his recovery decisions. "Now, I consult my HRV before deciding whether to rest or train," he explains. The approach paid off: he reports feeling more balanced and later launched an app focused on stress tracking via HRV.
Why variability matters more than regularity
Deepak Bhatt, director of Mount Sinai Fuster Heart Hospital in New York, clarifies that while extreme irregularity signals dangerous arrhythmias, healthy hearts exhibit slight beat-to-beat variations. "Generally, higher variability is preferable," he notes, though ideal scores depend on age, sex, and fitness level.
Wearable brands report average HRV scores of 65 milliseconds for men and 62 for women among active users. Age plays a significant role: 25-year-olds average 78 milliseconds, compared to 44 for 55-year-olds. These figures approximate the average fluctuation in heartbeat intervals.
The science behind the numbers
HRV reflects the nervous system's ability to toggle between "fight-or-flight" stress responses and "rest-and-digest" relaxation. During physical exertion-like running-HRV drops as the heart maintains a steady, rapid pace. At rest, variability increases, with heartbeats naturally accelerating during inhalation and slowing during exhalation.
"A high HRV shows your system can quickly adapt heart rate and blood pressure to match circumstances," says Dennis Larsson, a postdoctoral researcher at Kiel University.
Dennis Larsson, Kiel University
Conversely, low HRV suggests the body is stuck in stress mode, a state linked to modern lifestyle pressures like work deadlines or traffic jams.
From fitness to mental health: HRV's broad applications
Cardiologists use HRV alongside other metrics to detect conditions like atrial fibrillation. Athletes monitor it to gauge recovery; a persistently low HRV after workouts may signal the need for extra rest.
A 2023 review found lower HRV in individuals with anxiety and depression, indicating chronic stress. Similar patterns appear in PTSD, dementia, and schizophrenia. Some treatments, like psychotherapy, have been shown to improve HRV, though effects vary-certain antidepressants may lower it.
HRV also offers clues about ageing. Chronic stress drives inflammation, a factor in age-related diseases. A 2024 review suggested HRV could predict inflammation levels and disease risk, positioning it as a potential ageing biomarker.
Can you improve your HRV?
Breathwork is a promising intervention. Tim Herzog, a Virginia-based psychologist and biofeedback practitioner, recommends 20-minute sessions of slow breathing (e.g., inhaling for 4 seconds, exhaling for 6) to regulate HRV. Studies link such practices to reduced symptoms in PTSD and depression, as well as benefits like better sleep and lower blood pressure.
However, experts debate whether HRV should be directly targeted. Larsson views it as a diagnostic tool, not a treatment focus. Bhatt agrees, noting that healthy behaviours like exercise and sleep often improve HRV, but the metric itself may not be the primary driver of wellness.
Practical tips for tracking HRV
Consumer wearables vary in accuracy. Karin Steere of the University of Puget Sound advises that chest-strap devices outperform wrist-based trackers. Regardless of the tool, she emphasizes tracking trends over time rather than fixating on single readings.
"Monitor your HRV daily and correlate it with behaviors like sleep or alcohol consumption," Steere suggests. "Over time, you'll recognize your baseline and how your body responds to different stressors."
Karin Steere, University of Puget Sound
Herzog adds that HRV can validate subjective feelings-like fatigue-or confirm progress in new fitness routines, even before physical changes appear.
Should everyone track HRV?
While HRV offers valuable insights, Bhatt cautions that simpler metrics-like heart rate, blood pressure, and cholesterol-may be more critical for most people. "Every adult should know these numbers," he says, noting that many overlook even these basics.
For those motivated to dive deeper, HRV can enhance self-awareness. But for others, it may add unnecessary complexity. As Bhatt puts it: "Don't let your heart skip a beat over it."
