What is the Best Measure of Heart Rate Variability?


The ideal measure of heart rate variability depends on your specific needs and circumstances. Factors such as the device used, recording duration and individual health and fitness levels influence accuracy.

HRV is a non-invasive measure of the variation in the time between consecutive heartbeats. It is influenced by the autonomic nervous system, which controls our “fight or flight” and “rest and digest” responses. A higher HRV indicates that the autonomic nervous system is functioning well and that the body is able to adapt to stress effectively.

HRV can be used to assess overall health, fitness, and stress levels. It can also be used to track recovery from exercise and illness and to optimize training performance.

When determining the best measure of HRV, there are several factors to consider, including:

  • Sensitivity: Some measures of HRV are more sensitive to subtle changes in heart rate than others.
  • Stability: Some measures of HRV are more stable against noise and artifacts.
  • Ease of use: Some measures of HRV are easier to collect and interpret than others.

Bryan Johnson, a serial entrepreneur and founder of Kernel, is a vocal advocate for HRV tracking. He believes that HRV can help us optimize our health, fitness, and performance.

“HRV is like a window into our body’s state,” says Johnson. “By tracking our HRV, we can learn how our bodies are responding to stress, exercise, and other factors. This information can help us make better decisions about our lifestyle and training.”

In the Diary of a CEO podcast with Steven Bartlett, Bryan Johnson explained that HRV is a representation of whether you are in a state of calm or stress. A higher HRV is generally considered better than a lower one, as it signifies the ability to efficiently transition between these states.

Bryan Johnson has experimented with various devices to improve his HRV. Some of the devices he has tried include Sensate, a vibrational device placed on the chest; Pulsetto, which uses vibration on the vagus nerve; and Neural Stem, which is positioned on the left tragus. Despite his relentless efforts in maintaining his health and wellness, Johnson expresses his frustration with the difficulty of improving his HRV. He speculates that his past struggles with depression and stress may have left a lasting impact, making it hard to recover fully. Thus, he remains on the quest to find advanced solutions that go beyond diet, exercise, routines, and sleep to boost HRV.

If you’re someone who is interested in taking control of your own health and well-being by using HRV, read on to find out more.

Different Ways to Measure HRV

Best Measure of Heart Rate Variability

There are various methods for measuring HRV, including:

  • Chest Straps: Known for their accuracy, chest straps provide direct contact with the heart.
  • Optical Sensors: Common in wearables like smartwatches, these use light to estimate HRV by measuring blood flow in the wrist or finger.
  • Smartphones: Several smartphone apps utilize the camera to measure blood flow in the fingertip.

Exploring Time-Domain Measures

In the time-domain measures, there are three key aspects, notably:

RMSSD – The Vagal Whisperer

The Root Mean Square of Successive R-R Intervals (RMSSD) is exquisitely sensitive, capturing subtle heart rate variations. It offers insights into the parasympathetic nervous system’s activity, governing the “rest and digest” mode.

SDNN – The Steady Hand

The Standard Deviation of Normal-to-Normal R-R Intervals (SDNN) provides a robust metric, measuring overall heart rate variability. It offers stability against noise and artifacts, even though it’s less sensitive to beat-to-beat changes.

pNN50 – The Beat Jumper

Percentage of Normal-to-Normal R-R Intervals differing by more than 50 milliseconds (pNN50) count heartbeats deviating significantly from the preceding one, revealing cardiac vagal control.

MeasureDescriptionSensitivity to beat-to-beat changesStability against noise and artifacts
RMSSDRoot Mean Square of Successive R-R IntervalsVery sensitiveLess stable
SDNNStandard Deviation of Normal-to-Normal R-R IntervalsSomewhat sensitiveMore stable
pNN50Percentage of Normal-to-Normal R-R Intervals differing by more than 50 millisecondsLess sensitiveMore stable

Unpacking Frequency-Domain Measures

In the frequency-domain measures, the heart’s rhythm resembles a musical composition, categorized into three bands:

HF – The Vagus Serenade

The High-Frequency (HF) band (0.15-0.4 Hz) delivers a delicate serenade from the vagus nerve, showcasing the parasympathetic system’s tranquility.

LF – The Rhythmic Tango

The Low-Frequency (LF) band (0.04-0.15 Hz) resembles a rhythmic tango, where both sympathetic and parasympathetic systems engage, portraying autonomic balance.

VLF – The Deep Bass Notes

The Very Low-Frequency (VLF) band (<0.04 Hz) delves into the deep bass notes of the autonomic orchestra, shaped by autonomic and thermoregulatory influences.

LF/HF Ratio – The Autonomic Balance

The LF/HF ratio, an intriguing measure, gauges the balance between the sympathetic and parasympathetic systems. A lower ratio signifies parasympathetic dominance, while a higher ratio suggests increased sympathetic activity.

Applications of HRV

HRV serves various purposes, including:

  • Monitoring Training Load: To ensure athletes avoid overtraining.
  • Tracking Recovery: For gauging recovery from training and illness.
  • Assessing Stress Levels: To identify potential health problems.

Choosing the Best Measure of HRV

The choice of the best HRV measure hinges on your goals:

  • For a holistic assessment of health and fitness, RMSSD takes the spotlight.
  • If vagal tone assessment is your aim, RMSSD and pNN50 are your top choices.
  • To explore autonomic balance intricacies, the LF/HF ratio shines.

Remember, HRV is influenced by factors like age, fitness level, stress, and medications. It’s essential to compare your measurements to baseline or reference values for similar populations.

Read About: Anxiety Disorders and Cardiovascular Health – The Role of Heart Rate Variability

Trusted HRV Monitoring Brands

Several reputable brands offer HRV monitoring devices and apps, including:

  • Polar
  • Garmin
  • Wahoo
  • Oura
  • Apple
  • Fitbit


In the grand symphony of our bodies, HRV serves as a conductor, directing us towards insights into our overall health, fitness, and stress levels. It’s a versatile tool, offering different measures to cater to your specific objectives, be it general health, vagal tone, or autonomic balance. If you choose to embark on this journey and track your HRV, ensure you select a validated and accurate device or app. Your heart’s rhythm holds the key to understanding and enhancing your well-being, and HRV is the master key to unlock its secrets.

Note: HRV is a complex metric, and personalized advice from a doctor or qualified health professional is essential for interpreting and improving your health and fitness using HRV.


D’Angelo, J., Ritchie, S. D., Oddson, B., Gagnon, D. D., Mrozewski, T., Little, J., Nault, S., & Tchounwou, P. B. (2023). Using heart rate variability methods for health-related outcomes in outdoor contexts: A scoping review of empirical studies. International Journal of Environmental Research and Public Health, 20(2), 1330.


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