Though common indicators of “stress”, “energy”, and “performance”, usually found in health-tracking apps, are often considered by the general public to be nothing short of a marketing ploy, this opinion is overconfidently incorrect. 

The point is, it would be appropriate to have these indicators explained from the physiological point of view so that nothing is left unanswered and untold. So, let’s have the show on the road.

What represents the basis of the methodology of HRV analysis?

How to measure heart rate variability? What do the indicators such as “Energy” or “Stress” mean in HRV equipment, and is it possible to measure the body’s charge level as if it was a smartphone? Let’s try to explain the mechanism as trivial as possible.

The analysis is based upon the heart rate, or rather, the variability between heartbeats. What “variability” itself means is that at an average 60 beats per minute heart rate, the gap between the individual beats can in some cases be less than a second, and in some – more.

The heart rate variability normal values can be presented in the rhythmogram. Welltory app is perfect for fast measuring but with deep understanding.  Upon further investigation, the wave structure of HRV is revealed. In this case, three main wave frequencies are differentiated:

  • Short waves (High-Frequency Waves or HF waves) characterize the parasympathetic nervous system’s impact, responsible for maintaining homeostasis. These waves reflect the influence of the nervus vagus (here), which brings parasympathetic impulsion from the brain to the heart; 
  • Long waves (Low-Frequency Waves or LF waves) reflect the impact of the sympathetic nervous system. As a general rule of thumb, the sympathetic nervous system is responsible for every single reaction that takes part in the “fight or flight” response;
  • Very long waves (Very Low-Frequency Waves or VLF-waves) reflect the humoral system’s impact, regulating the synthesis and release in the bloodstream of the hormones or other hormone-like substances. Since this process is relatively time-consuming, humoral regulation effects only kick in after some time has already passed. Consequently, such regulation brings more substantial changes that are “deployed” smoothly over time.

Even further transformation of the data allows us to observe the spectrogram, determining the level of impact of each of the systems on your heart rate. It means that you can clearly understand which of the systems affects you at the time of measurement to a greater extent:

 – the sympathetic system (stress),

 – the parasympathetic system (recovery from stress)

 – or the humoral system (hormonal intervention when both sympathetic and parasympathetic influences are insufficient).

So, what exactly do tabs like “Stress” or “Recovery” mean? 

Energy (also known as “Total Power”)

Total Power is calculated using the formula TP = VLF + LF + HF. While evaluating this indicator, you see the Total Power of all three frequency ranges of your heart rate. In general, this indicator shows the working capacity of your adaptive systems. It is the “charge level” of your body. The morning TP measurements are often higher than in the evening since the body gets tired during the day.

With this indicator’s help, you can track your complex physiological state and the body’s readiness for additional physical, intellectual and emotional overload (you answer whether the upcoming physical training or an exciting presentation will benefit your health). It is also necessary to know that both too low and too high TP values ​​are critical and indicate either a lack of Power or an “overvoltage” of adaptation systems.


Stress reflects data from the sympathetic system (LF waves). The indicator measures the degree to which you experience tension in response to a stressful factor. It is essential to understand that stress derived in HRV methodology is not psychological but direct physiological, being the logical outcome of stress-inducing signals. Both the absence and the overdose of stress are equally critical for the body: it is crucial to keep the indicator balanced to avoid a general deterioration in the health status.


More often than not, “Recovery” means the RMSSD indicator. It shows the parasympathetic system’s state responsible for the body’s homeostasis and recovery after stress. A high RMSSD indicates a high degree of recovery of the body and its readiness for regular and heavy loads. Yet, if the tendency has shifted towards lower values, you need to rest more and allow the body to recover. This indicator is especially popular among amateur and professional athletes, as it helps to regulate the load, monitor the progress or degradation of physical form. It may as well be used as a meditation tracker or with a sleep analysis app. 

How to start measuring heart rate variability?

You can start gathering related data even with your smartphone’s camera – with the help of specific apps, of course. The problem is that while it is convenient, it causes a large amount of noise in the specter, and as a result, you have a greater chance of getting incorrect data. 

Alternatively, you can choose from a large market of recording gadgets, being both standalone and integrated into the fitness-trackers like Apple Watch HRV measurements, either electrical or optical. 

As a matter of fact, you will need some “blood pressure and heart rate app” to interpret the existing numbers and provide the results as easily understandable conclusions. There is, to put it mildly, quite a lot of such apps in app stores – which one should be given a try first? 

In my humble opinion, Welltory will be your best bet, primarily due to the fact of its incredible user-friendliness. It presents the users precisely the “Performance”, “Energy”, and “Stress” tabs they will need. Additionally, Welltory is free to use for these basic assessments. 

So, what is there left to wait?

Give heart rate variability a try, and start improving your habits as you see fit. Just be careful not to substitute your rationality and common sense with just plain numbers. As always, moderation is the key.