The heart rate variability measurement shows us how well our autonomic nervous system is set up. Roughly speaking, our autonomic nervous system consists of two parts - the sympathetic nervous system (tension) and the parasympathetic nervous system (relaxation). The autonomic nervous system can be seen as a higher-level control center that uses nerves to control and regulate processes and functions in the body - more precisely: our organs and organ systems - and at best keeps them in a certain balance.