What Is HRV?
Heart rate variability (HRV) refers to the measure of the variation in time between each heartbeat. Though the heart may seem to beat evenly, the time between beats can vary by milliseconds. Heart rate variability is not the same as a heart rate, which is how many times a person’s heartbeats each minute.
Everyone has their own distinctive HRV, so it cannot be measured against a chart, range, or averages. It is normal for a person’s HRV to change from day to day and from season to season. A person’s age, gender, and even circadian rhythm can affect HRV.
The variability in a person’s heart rate is connected to the autonomic nervous system (ANS), which is subdivided into two main components:
- The sympathetic nervous system, which is also called the “fight-or-flight” mechanism
- The parasympathetic nervous system, which is responsible for the relaxation response, in which the body can recover and “rest and digest”
The autonomic nervous system helps keep the body in balance and it helps us respond effectively to stress, unhealthy diet, poor sleep, dysfunctional relationships, isolation or solitude, overtraining, or lack of exercise. When these triggers become chronic, the ANS is thrown off-balance and the heart rate variability can be affected. This is why it can be a good indicator of overall stress or health.
- High HRV is associated with the parasympathetic response of rest-and-digest
- It is a good indicator of a person’s general fitness and good recovery
- Low HRV is associated with the sympathetic nervous system and the fight-or-flight response
- It can be a sign of stress, illness, poor sleep, or overtraining
- It may also be low during high intensity exercise, when the body is stressed, but it will return to normal when the activity is over
- A low HRV can be used as a predictor of risk after a heart attack and as an early warning sign of diabetic neuropathy
How to Track HRV
Tracking HRV can help people learn what stressors are present in their life and how to better cope with them, for example, if HRV is low, it may mean rest is in order.
Heart rate variability can be tracked in several ways:
- Electrocardiogram (ECG or EKG): performed in a medical setting, this is the most accurate way to measure HRV
- Chest strap heart monitors: the best way to measure HRV at home
- Watches and apps: the accuracy of these vary widely and they are not as reliable as chest strap heart monitors or an electrocardiogram
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