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Cardiac Watch User Manual

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A Quick Guide to Understanding HRV or Heart Rate Variability…

This article will explain what HRV is and why it’s an important tool to helping you understand your overall health.  In this article we will discuss the following

  • What Heart Rate Variability Is.
  • Why you shouldn’t compare your heart rate variability to anyone else’s HRV
  • What HRV tells you about your body and wellness.
  • What you can learn from tracking your HRV

Over the past decade, science has discovered that the tracking and analysis of Heart Rate Variability ( HRV ) is an increasingly important method to predicting and evaluating the healthy function of a persons cardiac condition and general health.  There is always an ongoing struggle to understand cardio-vascular system diseases as well as problems and at the core of this research is the understanding about how the body’s natural electrical current – and in particular the human heart acts as it’s own stand alone  “power plant” with nodes that generate nerve impulses to cause the heart wall to contract and pump blood.  The contractions – or better know as heart beats – are affected by many factors including stress, diet, sleep levels, over all physical shape and so forth.   It’s important to remember that your HRV is as unique to you as your finger print is.

Related Reading:  Harvard Medical School says HRV is a new way to track over all health

So Just What is Heart Rate Variability ?

Heart Rate Variability is a complex subject, but in it’s most basic terms, it is the measurement of the space – or time – that is between heart beats.  A heart that beats sixty times in one minute does not necessarily mean that it beat exactly once ever second – rather, there is variation among the intervals between your heartbeats. The interval between your successive heartbeats can be, for example, 0.75 seconds between some two succeeding beats and 1.15 seconds between the next two.  For people with a wide variation in their heart beats, it is possible to actually feel the difference.

To further complicate this, depending on both internal and external circumstances at any given point throughout the day, a person’s Heart Rate Variability will change.  With that said, HRV is a reflection of the functioning cardio vascular system as a whole and how it is interacting with the body.  It is this knowledge and discovery that has lead scientists to understand how HRV analysis can help predict cardiovascular disease, the chance of sudden death by cardiac failure ( heart attack ) and even impact the physical performance of athletes.

HRV is non-evasive and relatively simple method to measure and the evaluate the effectiveness of the interaction of the cardiovascular system as it pertains to other body systems.  Not only does this provide an overall assessment of cardiovascular health as demonstrated, but also how capable the heart is able to react to the stresses of daily life.   This provides scientists the ability to measure and examine an overall assessment of the patient’s condition, as demonstrated by vital parameters of the physiological functions control, including the functional reserves of control mechanisms, and autonomic balance.

Understanding The Cardiac Watch and the Measurement of Variability

The Cardiac Watch provides detailed reporting on the measurement of HRV, including the most prominent number displayed on the smart phone app screen.  In the screen shot below taken from app, you can see that my most current measure of HRV was a sum total of 30.    A lower number indicates a low rate of variability while a higher number reflects a higher rate or HRV.    You might be tempted to assume that a lower rate of variability is desirable which isn’t always the case.  In general,  a higher heart rate variability sum is an indication of overall health and general fitness. Because your HRV rate is a reflection of how your heart is reacting to the changes your body faces during the day, it can then by in many cases used as a tool to provide insight into your overall well being.

Every Person’s HRV is Unique

It’s important that users should not compare their HRV to others as heart rate variability is affected by a number of factors such as age, hormones and the overall body functions, as well as lifestyle. We also know that heart rates, and variability are higher typically higher in women than men.

It’s also equally as important to know that there are no set or static guidelines for optimal HRV values rather it’s the measurement and analysis of how the heart is beating when impacted by both external and internal factors.

In the screen shot above, you can see in the graph section of the app report the orange line which represents my heart beat.  In this case it stayed relatively consistent around 79 beats per minute.  The green line reflects how varied the timing was in between heart beats during a 60 second measurement.   Keep in mind during this test, I was stationary at a desk writing this article. The up and down of the green line represents the changes in HRV during the test.   The pNN20 number is the amount of times a variation was detected that exceeded 20 milliseconds which in this case was 76 times – essentially meaning my heart rate beating pattern was different nearly every beat of my heart.  The type of variability indicated by HRV is perfectly normal and considered in many cases desirable.

So What Causes Variations in Your Heart Beats ?

To understand heart rate variability, we need to first discuss the body’s nervous system and heart rate as HRV is a reflection of what is called the autonomic nervous system.

The autonomic nervous system regulates critical biological systems including heart rate, respiration rate and even digestion. The autonomic nervous system has what is called a parasympathetic (rest) and a sympathetic (activation) branch.

Heart rate variability is a measurement between how both branches are functioning with an emphasis on parasympathetic.

When your heart beats, the greater the resting status it is in ( parasympathetic.) the more time there is for variations in the space between heart beats.   When you are active and putting a demand on the sympathetic branch of the heart, your heart beat increases there by creating less room for variations between successive heart beats.  When your heart is neither impacted by rest or activation of your autonomic nervous system, your general heart rate is called the Intrinsic Heart Rate.  For most people this heart rate is between 70 and 100 beats per minute but varies based on the individual.

This means then when you are at rest and the parasympathetic branch is active and the sympathetic branch is less active or inactive, your heart rate is lower and HRV measurement is going to higher.

The key is to watch your own baseline and typical HRV readings and interpret them with how you are feeling, your activity levels ( based on your own normal activities such as walking, going shopping, mowing the grass, going for a bike ride etc. )  Baseline is the typical normal average you see during your tests.

For example…

  • Your HRV may drop to a lower number during or shortly after strenuous activity.  ( Strenuous activity for you as every ones definition is different )  Your HRV should jump back up to normal baseline levels.  If it takes longer to return to normal, this can indicate your body is not ready to take on the next strenuous challenge.
  • If you are not sleeping well your HRV may decrease.  Use the Cardiac Watch’s Sleep Tracking Feature to test your REM deep sleep patterns.
  • Dehydration will decrease your HRV but will jump back quickly with good hydration.
  • If you are stressed or filled with anxiety, your HRV may drop below normal baseline levels and strenuous activity might not be the best idea until you feel better.
  • It isn’t uncommon to see your HRV drop shortly before you get ill with a cold or flu – even before any symptoms.  If you do get sick, your HRV can remain low for several days after the symptoms are gone which tells you that your body is still recovering and you should take it easy.
  • Smoking and alcohol will affect your HRV short term.

The take away point is that a low HRV number in comparison to your BASELINE HRV RATE can indicate your body’s not at optimum strength or functioning at 100%.

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