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What is HRV and How Does it Affect Your Health?

What is heart rate variability?

Heart rate variability (HRV) is a measure of the autonomic nervous system. Your autonomic nervous system (ANS) is the body’s main control system for regulation. It controls all things automatic (breathing, blood flow, hormones, immune function, digestion). HRV measurement is accurate, non-invasive and considered the most comprehensive biomarker of health and longevity.

Specifically, HRV is a measurement of the variation in time between successful heartbeats.

To understand HRV, it’s important to know that the heart doesn’t act like a metronome. For example, a resting heart rate of 60 beats per minute suggests 1 beat every second, when in reality there are millisecond variations between each heartbeat. Some beats are 0.8 seconds apart, while others are 1.2.

Interestingly, the healthiest hearts don’t have more steady and consistent intervals between heartbeats. Instead, healthy hearts react and recover from stressors quickly and efficiently, causing heartbeat intervals to vary tremendously. Because of that, a high HRV score is healthiest.

  • High HRV scores: correlate with resilience, longevity, fitness and strong mental health.
  • Low HRV scores: correlate with inflammation, poor health markers, reduced fitness and increased risk of chronic disease.

HRV is not the same as heart rate

Heart rate measures how many times your heart beats per minute, while HRV measures the changes/variability between heartbeats. Heart rate can easily be measured by resting your finger on the inside of your wrist. HRV requires a specific device that’s sensitive enough to calculate the exact number of milliseconds between each heartbeat.

How the body responds to and recovers from stress

At rest, the human body is participating in a complex balancing act called homeostasis as it responds to the dynamic conditions of your life and surroundings. The variability we experience between heartbeats is a direct result of the autonomic nervous system fine-tuning our physiology in response to life’s ups and downs. The ANS achieves this through its two branches:

  • Sympathetic nervous system (SNS): fight-or-flight stress response, needed for short-term survival. The SNS is activated when we exercise, perform challenging mental tasks, get in an argument or sit in heavy traffic.
  • Parasympathetic nervous system (PNS): rest-and-digest responses, needed for long-term survival. The PNS is activated when our body is recovering and conserving energy.

Think of your body like a car. Your SNS is like the accelerator, revving you up in stressful situations. Your PNS is like the braking system, returning you to resting state after the stressor has passed. For our body to function optimally, both our accelerator (SNS) and braking system (PSN) need to be working. This means that we can respond to stress quickly and return to normal just as fast.

How does HRV relate to overall wellbeing?

Remember that the SNS is designed for short-term survival, however this acute response can become chronic in the presence of ongoing stress from things in our everyday lives (work, relationships, finances, environment, diet and lifestyle choices.)

A high HRV indicates that your body is equipped and resilient to respond to stress well. A low HRV isn’t necessarily a bad thing. It could simply signal that a lifestyle change is warranted (more sleep, work less hours, eat more nutrient dense food).

Tracking HRV helps you:

  • Create a powerful feedback loop that brings awareness of how your lifestyle impacts overall health
  • Prevent burnout from stress
  • Identify risk of illness or injury to accelerate recovery and healing
  • Track progress to see when your health, fitness and wellbeing are improving or declining
  • Become more aware of how your body is adapting to the stress of everyday life

What is a normal HRV?

HRV is based on individual circumstances, lifestyle choices, age and sex which is why it’s emphasized to monitor personal trends and improvement over comparing your reading with someone else’s. This can be a particularly useful health metric as you start incorporating healthy changes into your daily routine.

However, it can be helpful to see how you compare to others in your age group.