What Is HRV?
HRV stands for Heart Rate Variability. It is a measurement of your heartbeat’s variability, which indicates how well your body adapts to stressors. Your heart beats at regular intervals with different rhythms depending on whether it is working or resting. When you are under stress, such as during exercise or emotional distress, your heart rate may fluctuate from one beat to another, resulting in a variation between beats (or “ramping”). HRV measures the variations in your heartbeat’s rhythm over time.
The term “heartbeat” refers to the beating of your heart. The term “rhythm” refers to the pattern of beats within a beat-to-beat interval. There are many types of rhythms, but they all have one thing in common: They vary from beat to beat, rather than staying constant throughout a period of time. For example, if you were to count up to ten in your head while counting down from five, the first number would be one and the last number would be nine.
If you counted up to twenty-five in your head while counting down from five, the first number would be two and the last number would be fifteen. These patterns of beats do not change throughout a period of time; instead they vary from beat to beat. The former is an example of a fixed rhythm, while the latter is an example of a non-fixed rhythm. The variation in each beat from one to the next is known as “beat-to-beat variability.”
A good way to visualize this is by thinking about the metronome used by musicians and music teachers. A metronome consists of two elements: a pendulum (which oscillates back and forth) and a mechanism that clicks at a regular interval. The musical term “beat” refers to the clicking of the metronome mechanism, and a “beat-to-beat interval” is the period of time between one click and the next.
When your heart beats, it does so in much the same way as a metronome’s pendulum: It contracts, and then relaxes, over and over again.
Sources & references used in this article:
Amygdala and heart rate variability responses from listening to emotionally intense parts of a story by M Wallentin, AH Nielsen, P Vuust, A Dohn, A Roepstorff… – Neuroimage, 2011 – Elsevier
Individual endurance training prescription with heart rate variability by V Vesterinen, A Nummela, I Heikura, T Laine… – Medicine and science in …, 2016 – jyx.jyu.fi
Effects of exercise intensity and duration on nocturnal heart rate variability and sleep quality by T Myllymäki, H Rusko, H Syväoja, T Juuti… – European journal of …, 2012 – Springer
Basic notions of heart rate variability and its clinical applicability by L Vanderlei, C Pastre, R Hoshi, T Carvalho… – Brazilian Journal of …, 2009 – bjcvs.org
High-intensity interval exercise training improves heart rate variability in patients following percutaneous coronary intervention for angina pectoris by PS Munk, N Butt, AI Larsen – International journal of cardiology, 2010 – Elsevier