In the last 4 weeks I have been doing a lot of research when it comes to HRV, along any research I have been doing I have also been tracking my own so that I have experience of exactly how this works. I use an app called Elite HRV and just the last two weeks the new Apple watch. With the Elite HRV app I have been using a H10 Polar chest strap. I do this every single morning as soon as I wake up.
What Is Heart Rate Variability (HRV)?
A healthy heart beat contains healthy irregularities. Even if your heart rate is, say, 60 beats per minute, that doesn’t mean that your heart beats once every second or at one second intervals like a clock.
Rather, there is variation among the intervals between your heartbeats. The interval between your successive heartbeats can be, for example, 0.85 seconds between some two succeeding beats and 1.35 seconds between some other two.
Even though the difference is measured in parts of seconds, you can actually feel the difference.
Here’s a tip for anyone who wants to experience it: place a finger gently on your neck or wrist and find your pulse. You should feel that the longest intervals take place when you exhale, and the shortest intervals when you inhale.
How you calculate heart rate variability depends on what technology you use. Using an ECG, or electrocardiogram, it’s typically the R peak in the QRS complex that marks a heartbeat. Hence, the intervals between heartbeats are called R-R intervals.
With the H10 Polar heart strap, the Orthostatic Test is a test that monitors the training-induced changes in the function of your autonomic nervous system. It measures your heart rate and RR intervals both at rest and standing up and displays these values as a result in the Elite HRV App.
There are many factors that affect the results of the Orthostatic Test, such as mental stress, sleep, latent illness and environmental changes (temperature, altitude) to mention a few.
Changes in heart rate and HRV are always individual, and this is why you should do the test regularly to establish your individual baseline. To make sure that your results are as reliable as possible, you need to perform the test in similar conditions every time.
I do mine every morning, I get up, have a shower, brush my teeth and after that I lay in bed and do the 2 minute test, breathing normally.
Once you have your baseline set, you can start following the results. the Elite HRV app shows you your average heart rate and HRV values, and if they are slowly increasing over time, you’re probably making steady progress in your training. Sudden deviations from the averages could signify that something is off-balance.
DEFINING HEART RATE VARIABILITY
Heart Rate Variability is a measure which indicates the variation in your heartbeats within a specific timeframe. The unit of measurement is milliseconds (ms).
If the intervals between your heartbeats are rather constant, your HRV is low.If their length variates, your HRV is high.
There are different ways to calculate HRV, but they all have to do with the amount of variation in the intervals between heartbeats. The most commonly used HRV formula is rMSSD (Root Mean Square of the Successive Differences).
The figure below is an example of interbeat intervals in milliseconds.
Why Is Heart Rate Variability an Important Measure?
To understand HRV, we first need to understand our nervous system and heart rate. Heart rate variability can be traced back to our autonomic nervous system.
The autonomic nervous system regulates very important systems in our body, including heart and respiration rate and digestion. The autonomic nervous system has a parasympathetic (rest) and a sympathetic (activation) branch. Heart rate variability is an indicator that both branches are functioning – the parasympathetic in particular.
Intrinsic heart rate is measured in the condition in which neither parasympathetic nor sympathetic regulation is present. When completely blocked from autonomic regulation, a healthy heart contracts at a rate of about 100 beats per minute (the number is individual, however).
Parasympathetic regulation lowers your heart rate from the intrinsic level, giving more room for variability between successive heartbeats. Parasympathetic regulation causes almost immediate changes that affect only a few beats at a time, after which the heart rate returns towards the intrinsic rate. Sympathetic regulation elevates your heart rate from the intrinsic level, and there is less room for variability between successive heartbeats. Sympathetic regulation affects several consecutive heart beats.
Put these together and we can formulate a rule that when the rest-related parasympathetic branch is active and the sympathetic branch is inactive, your heart rate is lower and HRV higher. Factors such as stress can lead to the withdrawal of parasympathetic activity, or activation of sympathetic branch even when you are resting, both leading to elevated heart rate and lowered HRV.
HRV AND CARDIOVASCULAR TRAINING
Heart rate variability has been studied, for example, in the context of cardiovascular training.
When you start regular cardiovascular training, one of the fastest positive adaptations of your body is increased blood plasma volume, and subsequently increased stroke volume. As a result, your heart can keep the blood flowing and maintain adequate blood pressure at a lower heart rate. And mentioned above, lower heart rate is regulated by the parasympathetic branch. Parasympathetic regulation causes longer interbeat intervals and elevated HRV.
In the long term, regular exercise also strengthens the heart muscle, which once again means lower HR and higher HRV.
On the whole, high heart rate variability is an indication of especially cardiovascular, but also overall health as well as general fitness. Generally speaking, it tells us how recovered and ready we are for the day. Also, HRV can react to changes in our body even earlier than heart rate. This makes it a particularly sensitive tool that gives us insights into our wellbeing.
Your Heart Rate Variability Is Unique
You shouldn’t compare your heart rate variability with other people, because HRV is affected by a number of internal and external factors such as age, hormones and the overall body functions, as well as lifestyle. Furthermore, at a given heart rate, women typically have a higher heart rate variability than men.
There are no generic guidelines for optimal HRV values – which is understandable considering there are several ways to both track and calculate it. The HRV value given by Elite HRV (rMSSD5min) can range from anywhere below 20 to over 100 ms. HRV tends to be higher when you’re fit and healthy, but how high is high depends on the individual.
Instead of comparing your HRV values with someone else’s (even people of same age and gender), you should concentrate on your own HRV and its trends. Also, for your daily HRV values to be comparable with each other, they should be tracked with the same method and in similar conditions.
What Can You Learn From Your HRV?
Heart rate variability is one of the indicators of the state of your health and fitness, recovery and readiness. However, your HRV values, like your overall health and fitness, are a combination of several things, so pay attention to yourself and how you feel as a whole. HRV is a good indicator, but it’s still just one indicator. Don’t rely too much on it, or any other measure alone.
With that out of the way, here are some ways you can learn from your HRV values.
The first thing to pay attention to is your own HRV baseline. That is, your typical HRV when you’re feeling as you feel on average. Your baseline is the starting point for your HRV explorations. You will get an understanding of your HRV baseline after using the heart strap for a while.
After discovering your baseline, you’re ready to follow up how your lifestyle and health affect your HRV. If your HRV goes down, something might be burdening your body and/or mind. If your HRV goes up, something might be doing good for your body and/or mind.
Before increasing your training load significantly or making major changes to your nutrition, remember to consult your doctor – especially if you don’t feel well or if you suffer from long-term illnesses.
Homeostasis and stress
The autonomic nervous system is responsible for maintaining the body’s homeostatic environment. Any external influence that disrupts homeostatic equilibrium, at any level, will activate the sympathetic nervous system, which in turn mobilizes resources to fulfill the metabolic need.
Once the need is satisfied, the parasympathetic nervous system slows down the metabolism and brings the body back to its baseline. Both of these systems work together to act as the gas (sympathetic) and brake (parasympathetic) pedals in supplying the body’s metabolic fuel.
In a perfect world, environmental stressors would be kept to a minimum while sleep, nutrition, and training would be the predominant focus for everyone.
What are some of the sympathetic and parasympathetic overtraining symptoms?
Overtraining and under-recovery impacts the human body's energy equation due to large amounts of time spent in a sympathetic nervous system ("fight or flight” - energy expenditure) state and very little time spent in a parasympathetic nervous system ("rest and recover” - energy production) state. Poor quality sleep also impacts our brain function and performance.
When our body is under stress we are in the sympathetic (fight or flight mode) - Stress comes in many ways, training is one of them as is arguing with the guy that just cut you up in the middle of the road! Parasympathetic, is the opposite.
Below are some of the results of being in one or the other and what we can do about it.
HRV is to low
HRV is to high
For me this has been a revelation, I have been much more in sync with my body and I have listened to my body more, this has resulted in managing my training much better and my sessions have become much better.
This is something I will be using with some of my clients and with myself for the foreseeable future.