Heart function can be assessed using many parameters. One constantly gaining attention, mainly among people looking to track, understand and optimize their recovery and readiness, is heart rate variability (HRV). So, what is HRV all about and how can it help to improve your performance?
The usefulness of HRV has been evaluated across multiple studies, which have proved its effectiveness as an indicator of several health-related issues. However, it has only recently grabbed the attention of specialists, including athletes and coaches, but also the general public.
What Is Heart Rate Variability?
In a healthy heart, some irregularities in heartbeat can be observed, even if they are difficult to spot. Your calculated heart rate e.g. 70 beats per minute, doesn’t indicate regularity and, what is more, many variabilities can occur while recording or counting it. Some variations in the intervals between your heartbeats are completely physiological and can change depending on several factors. Despite the fact that these changes are measured in fractions of seconds, you can actually feel them, for example by putting your fingers on your neck and holding your breath while feeling the pulse. The intervals should become longer and longer, or, if you breathe more quickly, the intervals will shorten.
Assess Your Heart Rate Variability
HRV can be assessed using a few methods, for example ECG (looking at the distance between R waves in QRS complexes) or photoplethysmography (PPG) (where interbeat intervals are measured). One has to remember that variations in heartbeat are recorded within a specific timeframe, measured in milliseconds (ms), which depends on the method and device used to calculate HRV.
Poincare plot for 24h ECG signal
When it comes to HRV analysis, constant intervals between heartbeats indicate a low HRV. On the other hand, if the intervals between heartbeats change, then your HRV is high.
How Does Heart Rate Variability Correlate with the Neurological System?
At this point, one could ask if Heart Rate Variability is an important thing to measure. How can looking at your HRV be beneficial? Firstly, we should look more closely at the basic physiological patterns. Heart rate is strictly controlled by the autonomic nervous system, which can be divided into the parasympathetic (activated while resting) and sympathetic (activated during endurance or stress) branches. HRV indicates that both branches work in close collaboration and are in balance. During the vast majority of activities, like eating, sleeping or working on the computer, there is slightly more activity in the parasympathetic branch. Assuming that the nervous system is not influencing heart rate, the heart contracts approximately 100 times per minute, and, as is well known, a normal heartbeat is usually around 70 beats/min. To sum up, while at rest, heart rate is lower and therefore HRV higher, due to extra activity in the parasympathetic branch. However, several stress related factors can change the balance, showing a higher level of sympathetic branch activity and, as a result, an increased heart rate and lower HRV.
Optimize Your Performance Using Heart Rate Variability
As HRV has been studied in terms of physical activity, it has been established that regular activity, among several other behaviors, lowers resting heart rate. Consistent with what has been mentioned above, this can be translated into increased parasympathetic branch activity and longer interbeat intervals – meaning an elevated HRV.
From a wider perspective, HRV reveals information not only about cardiovascular, but also overall health. What is more, HRV can reflect changes in our body, even before heart rate, which makes it a particularly sensitive tool for providing insights into our wellbeing. However, HRV should not be compared between individuals as there are several factors which can influence it, such as sex, age, hormones, the overall functioning of the body, and lifestyle. Because of its recent appearance, there are no guidelines for optimal HRV values.
However, you can and should look at changes and trends in your HRV as this can help reveal information concerning your health and fitness. Still, as HRV is connected with lots of variables you should pay attention to yourself and use HRV as one of the tools to assess your condition, with the biggest role being how you feel in general. However, this doesn’t mean that it is useless – you can learn some things based on HRV. At the beginning, record your baseline HRV when you are feeling normal. Now you are ready to observe how your lifestyle, diet and stress affects your HRV. For example, you might realize that physical activity can lower your HRV, but also that it returns to normal quickly, which is a sign of regeneration. If the HRV stays low, it can indicate very intense training and the need for some time to recover.
Additionally, HRV can drop when becoming stressed or not sleeping well. Going further, both smoking and alcohol consumption reduce HRV, which seems consistent with the generally accepted unhealthy status of ethanol. Finally, HRV drops with dehydration and normalizes after rehydration, showing its helpfulness, for example, after a workout.
Stroke Prevention
Stroke can lead to lots of disturbing consequences, including speech problems and disability. It appears that every fifth stroke is connected with atrial fibrillation (AF). What is AF? AF is characterized by a loss of atrial function and, as a result, blood clots, which can travel via arteries to the brain resulting in brain ischemia. This is connected with an irregular heart rhythm, which can be sensed by both palpation and application assisted pulse assessment.
There are drugs which can prevent stroke in AF patients, but diagnosing patients with AF remains a problem, as some of them may be symptomless. This is where modern technologies, including HRV, enter the game. Taking into consideration the popularity of several devices, including smartphones and smartwatches, it seems natural to use them in the prevention of dangerous diseases. Among many benefits, one is the prolonged monitoring that is possible when compared with traditional methods. Of course, prolonged monitoring means more data, which may be problematic, but, fortunately, Artificial Intelligence (AI) provides support in this area, as do prepared algorithms . All of this just proves that modern technologies, including HRV, can help us to improve quality of life by stroke prevention.
Summary
HRV is a very useful tool which may be an interesting addition in helping us to better understand our bodies. Naturally, lots of people can gain from HRV observation, from those who are exercise-oriented to people at risk of stroke.