Basic Heart Rate Variability (HRV) is the change in time between successive heartbeats (also called inter-beat intervals, R-R intervals, N-N intervals, etc.).
Unlike Heart Rate (HR) that averages the number of heart beats per minute, HRV looks much closer at the small fluctuations of the heart that occur in response to internal and external events.
HRV is a direct link to your Autonomic Nervous System (ANS) and can therefore be used to gain insights into your nervous system, stress and recovery activity.
Your Nervous System in a Nutshell
Your Autonomic Nervous System controls your body’s unconscious processes (with the help of the endocrine system, etc.) such as blood sugar, adrenaline, digestions, pupil dilation, heart rate, and much more. The ANS has two main branches: the Sympathetic Nervous System (SNS) and the Parasympathetic Nervous System (PNS).
The Sympathetic Nervous System controls your body’s “fight or flight” reactions in response to internal or external stressors. It stimulates blood glucose, pupil dilation (to see tigers better), slows digestion/peristalsis, and increases heart rate. The SNS is ideally activated to overcome short term stress situations and typically ignores long term health.
The Parasympathetic Nervous System controls your body’s “rest and digest” responses and is associated with recovery. Parasympathetic activation conserves energy, constricts pupils, aids digestion, and slows heart rate. The PNS is meant to help build for the long term and is needed to grow faster, stronger, healthier.
Both branches are always working and both are needed to maintain homeostasis in your body. With every single heartbeat, your nervous system is saying “slow down – speed up” based on feedback from all your senses, emotions, etc. A healthy nervous system has a balanced but strong push and pull between the Sympathetic and Parasympathetic branches.
More In-Depth Knowledge
The best way to learn more about HRV is to download the free app from the App Store or Play Store and receive a 50 page PDF guide covering more about the science and application of Heart Rate Variability.