Heart rate persons with coronary artery disease. The heart rate is rhythmically generated by the sinoatrial node. It is also influenced by central factors through sympathetic and parasympathetic nerves. Nervous influence over the heartrate is centralized within the two paired cardiovascular centres of the medulla oblongata. The cardioaccelerator regions stimulate activity via sympathetic stimulation of the cardioaccelerator nerves, and the cardioinhibitory centers decrease heart activity via parasympathetic stimulation as one component of the vagus nerve. During rest, both centers provide slight stimulation to the heart, contributing to autonomic tone. This is a similar concept to tone in skeletal muscles. Normally, vagal stimulation
Heart rate reference period is associated with a higher level of cardiac fitness. Heart rates that do not drop by more than 12 bpm one minute after stopping exercise are associated with an increased risk of death. Investigators of the Lipid Research Clinics Prevalence Study, which included 5,000 subjects, found that patients with an abnormal HR (defined as a decrease of 42 beats per minutes or less at two minutes post-exercise) had a mortality rate 2.5 times greater than patients with a normal recovery. Another study by Nishime et al. and featuring 9,454 patients followed for a median period of 5.2 years