Heart rate variability (HRV) offers insights into recovery from illness, injury or exercise, can track levels of physical and emotional stress, and even act as a predictor of cardiac failure. Advances in technology, including image sensors, now make HRV measurement accessible to anyone with a chest strap or smartphone.
Whereas heart rate provides beats per minute, variability shows the change in time gap between those cardiac contractions. Heartbeat is highly correlated with respiration: it speeds up as you breathe in and slows when you exhale — and this difference provides a measure of variability. But when the body is tired, the disparity in heart rate between inhalation and exhalation narrows.
HRV is a little more complicated to capture than traditional metrics because more precise instruments are required to detect, time and record beats of the heart, and then run the statistical analysis to calculate variability. Two patients can have exactly the same heart rate (HR) but differing gaps (HRV), so accuracy is crucial.
A major stumbling block is collating accurate and usable data. Other metrics such as temperature or blood pressure can be taken instantaneously, compared against population averages and acted upon immediately. HRV, on the other hand, is very individual and requires the collation of baseline figures over multiple days and in similar circumstances each time.
Incorporating HRV into daily life remains the biggest challenge. While a bevy of gadgets can now deliver a stress score each day, users need to resist the temptation to over-interpret a single day’s feedback or chase a “perfect number”. Doing so can lead to the deleterious nocebo effect.
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Advances in technology, including image sensors, now make HRV measurement accessible to anyone with a chest strap or smartphone.
