HEART RATE VARIABILITY: MONITORING OF AUTONOMIC NERVOUS SYSTEM ACTIVITY, DURING PHYSICAL ACTIVITY AND IN SPECIAL SITUATIONS

We can assess the autonomic nervous system using real-time non-invasive techniques. Heart rate variability (HRV) is a good option when compared to other techniques, such as molecular biology. Molecular techniques are invasive and have difficulties in their implementation and analysis, because of the rapid enzymatic action of cholinesterase and the inhibitory enzymes of mono amino oxidase that do not allow realtime evaluation of the concentrations of these neurotransmitters in blood. This chapter describes digital signal processing techniques that allow HRV analysis using time and frequency domains, as well as descriptions of implementing non-linear models. We note in the text the result of one of our investigations where we give an example of HRV use during the evaluation of physical activity, sports training, and inflammation. This example showed how pro-inflammatory substances act on the autonomic nervous system, generating responses at the cardiac, liver, and reticulum endothelial systems. Finally, we project the future use of HRV in exercise physiology and clinical physiology.