eshop mysasy facebook twitter twitter

HRV - heart rate variability

Although heart rate seems to be constant at rest, large or small differences can be observed in the distance between successive heart beats with high accuracy (up to 0.001 s).



These differences are caused by the impact of the autonomic nervous system on the heart frequency. By monitoring these differences and by their description, the total activity of the autonomic nervous system can be evaluated. 


SA HRV – Spectral analysis of heart frequency variability

The above-described differences in the distance between individual heartbeats are not quite regular. On the contrary, a very detailed analysis of a sufficiently long record of monitoring heart rate combined with monitoring of changes, caused by a chase of body position, enables accurate determining at what frequency the changes occur.

Low-frequency changes are usually due to sympathetic activity. They are more stable and, due to their low frequency, are only identifiable for a sufficiently long record.

Changes that are not identifiable by their low frequency in a shorter record can be of major importance. Methods using a record of fewer than 5 minutes are therefore unable to identify the sympathetic activity. Such records are lacking at least half of the relevant information.

High frequency changes are more likely caused by parasympathetic activity; evident more when lying down; and due to the higher frequency of occurrence they are more easily identifiable.

What affects the activity and balance of ANS and thus the results of HRV SA:

The basic level of ANS activity is genetically determined and is influenced throughout life by long-term and short-term effects such as:

  • health status (both chronic and acute)
  • the level of psychological stress (both long-term and acute)
  • level and composition of physical load/training
  • level, duration and quality of regeneration
  • proper diet
  • length and quality of sleep
  • altitude change
  • shifting in time zones


What it says and what can be the cause:


  • bad genetic disposition to respond and adapt to load - poor training
  • chronic disease
  • risk of or already existing injury
  • acute illness even at an early stage, before the outbreak of external manifestations
  • excessive mental stress
  • poor sleep quality
  • insufficient or inappropriate regeneration*
  • poor track (intensity x volume) of training
  • the onset of overload or overtraining
  • living issues (alcohol, poor nutrition, …)

* in the case of regularly trained persons, the total omission of the physical load during the regeneration phase can act as a "stress factor", which manifests in further, at first sight, paradoxical DECREASE OF HRV. 

High HRV

  • good genetic disposition to respond to and adapt to load - good trainability
  • absence or management of psychological stress
  • good sleep
  • proper nutrition and diet
  • optimal regeneration
  • optimal composition (intensity x volume) of training
  • readiness to undertake additional load


more information at mySASY academy

Get a new version of the training profile at a boot price and train smartly.