 Health of individuals is closely correlated to the stability of the autonomic nervous system ANS, a key system for maintaining homeostasis in any living species. Efficient computer tools allowed the opportunity to assess the intrinsic autonomic regulation of the ANS either directly or at a later time by an analysis of the heart rate variability HRV. These tools have become very powerful predictors of cardiovascular morbidity and neurological aging. Physical endurance training improves both maximal aerobic capacity and ANS activity. 