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 resting heart rate. Some methods of measurement of exercise intensity measure percentage of heart rate reserve. Additionally, as a person increases their cardiovascular fitness, their HR will drop, and the heart rate reserve will increase. Percentage of HR is equivalent to percentage of VO reserve. This is often used to gauge exercise intensity (first used in 1957 by Karvonen). Karvonen's study findings have been questioned, due to the following: For healthy people, the "Target Heart Rate" or "Training Heart Rate" (THR) is a desired range of heart rate reached during aerobic exercise which enables one's heart and lungs to receive