Heart Rate Monitors

The importance of heart rate to the assessment of physical performance in athletes has been well understood for more than 200 years; the tools for the collection and the measurement of such data were limited until the twentieth century.

The first electrocardiogram, a leap forward in the scientific ability to analyze the heart and its patterns, was developed in the 1920s by Dutch physiologist Willem Einhoven (1860–1927). The electrocardiogram is a device that permits the measurement of heart rate by way of a direct connection between a person's heart and the machine. Prior to the electrocardiogram, heart rate was typically measured through the manual application of the recorder's fingers on the skin of the person near the location of a major artery, such as at the wrist (radial artery) or the neck (carotid artery), to feel the pulse, count the rhythms, and measure the rate against a stopwatch.

The measurement of pulse by way of the fingers was an inaccurate method to gauge heart function. It was difficult to obtain statistical data concerning heart function while the athlete was participating in the activity. The portable heart monitor, a variation of the electrocardiogram, was developed as one of a number of biofeedback tools available to assist athletes in a number of ways.

To appreciate how the heart monitor is able to record heart rate, it is important to understand how the heart is stimulated to beat, as well as the relationship between the speed and frequency of heartbeat with the overall performance of the cardiovascular system. Heart rate, most commonly measured as the number of beats per minute, is directly tied to the cardiac output: the more the heart beats, the greater the volume of blood that is directed through the blood vessels of the body. As a very general physical proposition, the more blood available to transport energy products such as glucose, fluids, nutrients, as well as carry away wastes from the generation of energy, the greater the body's physical capabilities.

The heart beat rate is controlled by pace-making cells within the heart. The primary pace-making capacity is located within the sinoatrial node, known as the SA node. A secondary pace-making function is carried on at the arterioventricular node, the AV node. The actual transmission of the electrical current within the heart to stimulate its beat is influenced by a complex relationship between the

Heart rate monitor.
outflow of potassium ions from the heart muscle and a corresponding inflow of sodium ions. It is the detection and the measurement of this electrical current that is at the essence of a heart monitor.

The heart monitor has two parts. The monitor attaches to the body by means of a chest strap, with electrodes that make contact with the chest above the heart. The strap is secured by straps to ensure consistent recordings from the heart. The data gathered by the monitor is conveyed, either by a wire connection or, more commonly, through a wireless pathway to a display worn on the person's wrist. All heart monitors provide both instant "snapshots" of heart rate at a given time; the more sophisticated of heart monitors will also permit the user to simultaneously record such related physical data as predetermined personal heart rate zones, and whether the present workout is sufficiently difficult or moderate to ensure that the target zone is reached. Working at a target heart rate is useful knowledge for any athlete; it is data that is of prime importance to elite athletes, who seek to maximize their workout quality.

The heart rate monitor feedback concerning target rate is also of great utility to those athletes that have concerns about their heart health and wish to avoid an inadvertent or unplanned strain upon their heart. Middle-aged athletes that play a vigorous sport such as basketball or ice hockey are often vulnerable to a heart attack precipitated by overly vigorous play; the heart monitor can assist in keeping such athletes within a predetermined, safe use target.

The heart monitor can also provide related data as to estimated caloric consumption.

For athletes that engage in distance event sports, such as cross-country skiers, runners, and cyclists, there are heart monitors equipped with global positioning system (GPS) technology, which makes available sophisticated data as to the relationship between portions of a particular course and heart rate generated at those segments.

Heart rate data is stored in a downloadable format for further and future analysis, often in conjunction with other performance tools such as times achieved, weights lifted, or other indicators of physical performance. The most comprehensive of fitness assessments will involve the heart rate data produced through the use of a heart monitor, coupled with the testing of the related physical concepts, including the athlete's maximum oxygen uptake, stated as VO2max, the perspiration rate, and the recovery rate measured after specific activities.

SEE ALSO Cardiovascular system; Exercise, high intensity; Stationary bicycles, elliptical trainers, and other cardio training machines.