ABSTRACT
Autonomic control of heart rate is determined by the interplay between the excitatory influences of the sympathetic nervous system and inhibition by the parasympathetic system. These are modulated by many influences notably activity, emotion, and absorptive state, yet, in spite of the diversity of these influences, heart rate variability has emerged as a reliable index of autonomic control In adult life a reduction in heart rate variability can be a harbinger of coronary disease and it is associated with an increased hazard of sudden death. While this is well established in adults very little is known about heart rate variability in young people What little information is available has been gained in infants[1] or in disease[2]; there are very few normative data.
