Heart rate variability and Orthostatic Test | Let’s talk Polar

September 29, 2017

Did you know that September 29th is World Heart Day? Here at the Polar Blog we love hearts, of course, and in honor of World Heart Day we created a three-post blast about heart rate training and Polar Smart Coaching. Be prepared to dig deep (and this time we really mean deep) into the world of heart rate, sports and science. We’ll start the series by looking at the secrets of heart rate variability. Part two takes us behind the scenes of training load measurement, and in part three we learn about recovery monitoring. Get comfy, prepare yourself and enjoy the ride. Or run.

There are hundreds of love songs on how unrequited love makes the heart beat slow and heavy, and how the sight of the object of one’s desires turns the foolish heart into that of a hummingbird, beating 1,400 times a minute – or that’s how it feels, at least. But there aren’t that many, if any, songs about the time between those heartbeats. Yet if an educated, modern-day lyricist were to write a song, that’s exactly what she would write about. According to a plethora of recent studies, the frequency of heartbeats and the regularity of those beats reveal an astonishing amount of things about the carrier of that heart.

The time between the beats

Most people would be surprised to learn that even the strongest, healthiest of hearts doesn’t beat with the regularity of Swiss clockwork. Heart rate variability (HRV) – also commonly referred to as cycle length variability or RR variability – is the phenomenon of variation regarding the time interval between consecutive heartbeats. Even when a person’s heart rate is relatively stable – say, at a state of rest – the RR intervals (the times between heart beats) vary quite substantially.

Heart rate variability can provide information on several factors related to cardiovascular health or mental stress, and it can also reveal a person’s state and level of relaxation and sleep. This beat-to-beat interval has been the focus of an increasing number of studies, as reduced HRV has been found in groups of patients with health issues such as coronary heart disease, fibromyalgia, diabetes, congestive heart failure and even depression.

Heart rate variability and training

The interesting thing about heart rate variability for physically active people is its relationship to exercise. In fact, HRV has been shown to provide information on several factors related to cardiovascular health, aerobic fitness, and responsiveness to training. To put it simply, monitoring your HRV can help you see how your body is adapting to your training regime.

What, then, is a good, or ”ideal”, heart rate variability, and what is a cause for concern? Logically, it would make sense that a low variability would be the one to aim for. Since a low resting heart rate indicates a big, strong heart, then a low degree of variability must also signify that the heart is strong and doesn’t react easily by changing its pacing, right? Wrong. In general, a higher variability is related to improved health. When looking at things in the long term, high HRV indicates that the heart is functioning well, and that the autonomic nervous system is adapting to the demands placed on it. A lower HRV, in turn, can be a warning sign of illness or an abnormal and insufficient adaptation system. To simplify things again: if your HRV is slowly increasing over time, this probably means that your fitness is improving. Any sudden changes in HRV could indicate that you haven’t recovered properly, you’re under a lot of stress or you’re coming down with an illness.

So how can I measure my HRV?

First of all, HRV measurement requires ECG-based heart rate readings, so you’ll need a chest strap heart rate sensor, such as Polar H10. You’ll also need a Polar product that includes the Orthostatic Test, such as the Polar V800 GPS sportswatch or the Polar M460 GPS cycling computer. 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 Polar Flow.

There are many factors that affect the results of your 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 similiar conditions every time – we recommend that you take the test in the morning before breakfast.

Once you have your baseline set, you can start following the results. Polar Flow 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.

HEART RATE VARIABILITY IN A NUTSHELL

  • Is the time interval between heartbeats
  • Is affected by aerobic fitness
  • Other factors that affect HRV are a.a. age, genetics, time of day, and health status
  • A high HRV indicates a healthy heart
  • During exercise, HRV decreases as HR and exercise intensity increase
  • HRV also decreases during periods of mental stress
  • You can monitor your HRV with Polar’s Orthostatic Test, found on Polar V800 and Polar M460