Application of Optical Heart Rate Monitoring

Since the introduction of portable devices in 1957 by Dr. Norman Holter, heart rate (HR) monitors have been extensively used in clinical practices as a diagnostic and prognostic tool, mainly for cardiovascular diseases. In parallel, the use of HR monitoring devices by sport physiologists to analyze the response of the body to exercise or training stress and to evaluate the training level of athletes has gained popularity. With the increasing interest of consumers to health and wellness monitoring, an explosion of commercialized HR monitors based on various technologies has been observed during the last decade. This chapter will give an overview of the different techniques actually known to monitor HR, focusing in particular on the so-called photoplethysmographic (PPG) technique. The history of the PPG technique, its basics, including measurement principles, measurement sites, quality factors and its applications to sport, fitness, daily life, and healthcare, will be addressed in respective sections. The heart is the muscle in charge of pumping the blood throughout the blood vessels, namely the arteries and the veins carrying oxygenated and deoxygenated blood, respectively. The regulation of the rate at which the heart is pumping is mainly controlled by the autonomic nervous system. This system comprises sympathetic and parasympathetic (or vagal) functions, which are partially complementary. The sympathetic nervous system is responsible for increasing HR, constricting blood vessels, and other “stress” responses, while the parasympathetic system promotes maintenance of the body at rest (e.g., slowing