Valencell is continually asked by our customers how heart rate variability is measured and what can be done with the resulting measurements. Valencell believes any biometric indicators should be supported by scientific validation of those measurements to ensure they are providing real insights that users can count on. So to help answer these questions, we conducted a comprehensive scientific literature review around heart rate variability to understand what use cases and applications have been proven with scientific rigor. The results of that review can be found here. Dr. Chris Eschbach, Director of Valencell’s Biometrics Lab, discusses in more detail below.


What is Heart Rate Variability?

Heart rate variability (HRV) is gaining popularity in biometric wearables as a means to create more in-depth insights including measurements of stress, sleep, training status, and much more. In general, decreases in heart rate variability indicates some kind of negative general stress.

How is Heart Rate Variability measured and what can we do with it?

Assessment of the beat-to-beat variability or heart rate variability (HRV) can be an indicator of “stress” (physical and/or mental) on the body. The amount of variation in time (milliseconds) of the beat-to-beat interval is controlled by the nervous system with less variation under greater control of the sympathetic nervous system and more variation under greater control of the parasympathetic nervous system.


Stress and Heart Rate Variability

Stress is a state of physical, mental, and emotional strain on the body. One should not think of stress as a single event or experience but rather an accumulation of all circumstances occurring over time. Stressors from all sources have an additive effect on the body and will eventually lead to decreased mental and/or physical performance if not properly balanced with relaxation and/or recovery. These stressors include, but are not limited to, changes in the following: physical workload, sleep, diet, disease states, daily career and life tasks and interactions. The impact of the stressors on the body is monitored by HRV and related to fatigue (mental and work capacity) and readiness to perform mental and work tasks.


Heart Rate Variability Statistics

The individual baseline of RRi/PPi and related HRV metrics is not the same for all individuals and it cannot be assumed that data between individuals will show the same physiological response to similar stressors. Because of high day-to-day variability in environmental and homeostatic factors, results have been varied with regards to the influence of stress on HRV. To overcome this variability, it is helpful to analyze individual baseline HRV metrics. To help resolve challenges with the minute-to-minute and day-to-day variation, it is recommended to collect weekly and/or 7-day rolling averages, techniques which would have higher validity and statistical value than daily recordings of HRV.

If you have questions or would like more information on Heart Rate Variability, please reach out to