The Foundation of Heartify’s Personalized Insights



The breakthrough for HRV came in 1987 when Robert Kleiger’s landmark study proved patients with low HRV were 5 times more likely to die in the years immediately following a severe heart attack.
If you’ve ever put fingers on your neck or wrist to count your heart beats, you’re already familiar with PPG. Photoplethysmography (PPG) is a technique using light to illuminate finger skin tissue to measure the volume of blood circulating in your finger. We use this to measure your pulse, but also the time between heart beats (heart rate variability). Many products use PPG to measure your heart rate. The Apple Watch, FitBit and many iPhone health apps use this method.

Photoplethysmography (PPG)

Our Methodology

how it works


In 1965, an analysis of fetal ECGs showed that distressed fetus exhibited diminished HRV compared to non-distressed fetus.
A healthy heart isn’t like a metronome beating at a consistent interval! Your heart rate is controlled by the hypothalamus, a part of your brain. The hypothalamus, through the autonomic nervous system (ANS), sends signals to the rest of your body either to stimulate or to relax different bodily functions. To be specific, the ANS uses its sympathetic nervous system (stimulation) and parasympathetic nervous system (relaxation). For instance, when you exercise your hypothalamus uses the sympathetic nervous system to increase your heart rate.

Heart Rate Variability

What is HRV?

Heart Rate Variability (HRV) is measure of the variation in time between your heart beats. HRV tells a story of how your sympathetic and parasympathetic systems are changing your heart rate in response to everyday life. By analyzing the time between your heart beats, we can detect your stress and energy level as well as gauge your body’s ability to recover from stress.
When you rest, your hypothalamus uses the parasympathetic nervous system to decrease your heart rate. Your hypothalamus uses these systems to respond to every moment of your life. To be healthy and ready for life’s ups and downs, you need both systems need to work well!

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