Numerous factors can influence the sympathovagal balance and thus affect HRV. For example, with advancing age or some disease states, there is a decrease in parasympathetic tone at rest (19) or an increase in sympathetic nervous system outflow (8). This results in a disturbance in sympathovagal balance and a decrease in HRV. Some specific examples of diseases that promote a deceased in patients suffering from depression, following a myocardial infarction (19). Importantly research indicates that physical inactivity promotes a decrease in HRV (19). Therefore, investigation of the types of exercise and specific training programs that have positive influences on HRV has become an important area of research.