Heart rate recovery: a practical clinical indicator of abnormal cardiac autonomic function.

The autonomic nervous system (ANS) and cardiovascular function are intricately and closely related. One of the most frequently used diagnostic and prognostic tools for evaluating cardiovascular function is the exercise stress test. Exercise is associated with increased sympathetic and decreased parasympathetic activity and the period of recovery after maximum exercise is characterized by a combination of sympathetic withdrawal and parasympathetic reactivation, which are the two main arms of the ANS. Heart rate recovery after graded exercise is one of the commonly used techniques that reflects autonomic activity and predicts cardiovascular events and mortality, not only in cardiovascular system disorders, but also in various systemic disorders. In this article, the definition, applications and protocols of heart rate recovery and its value in various diseases, in addition to exercise physiology, the ANS and their relationship, will be discussed.