Heart rate monitor

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Photo of a heart rate monitor showing chest strap and watch
X-ray image of a chest strap (left: frontal view; right: side view). Visible is the circuit board, the antenna for data transfer, the battery and the connections to the electrodes in the adjoining belt at picture top and bottom.
Photo of a strapless heart rate monitor
Photo of a Polar RC3 GPS heart rate monitor watch - chest strap not shown
This article refers to a device used by non-scientists. For the article on the medical device performing a similar function, see Electrocardiography.

A heart rate monitor is a personal monitoring device that allows one to measure one's heart rate in real time or record the heart rate for later study. It is largely used by performers of various types of physical exercise.


Early models consisted of a monitoring box with a set of electrode leads which attached to the chest. The first wireless EKG heart rate monitor was invented in 1977 by Seppo Säynäjäkangas, founder of Polar Electro, as a training aid for the Finnish National Cross Country Ski team. As 'intensity training' became a popular concept in athletic circles in the mid-80s, retail sales of wireless personal heart monitors started from 1983.[1]


Modern heart rate monitors usually comprise two elements: a chest strap transmitter and a wrist receiver (which usually doubles as a watch) or mobile phone. In early plastic straps, water or liquid was required to get good performance. Later units have used conductive smart fabric with built-in microprocessors that analyze the EKG signal to determine heart rate.

Strapless heart rate monitors (often referred to as "wearables") now allow the user to just touch two sensors on a wristwatch display for a few seconds to view heart rate data. These are popular for comfort and ease of use, though they don't give as much detail as monitors that use a chest strap.

More advanced models offer measurements of heart rate variability, activity, and breathing rate to assess parameters relating to a subject's fitness. Sensor fusion algorithms allow these monitors to detect core temperature and dehydration.

Another style of heart rate monitor replaces the plastic around-the-chest strap with fabric sensors - the most common of these is a sports bra for women that includes sensors in the fabric.

In old versions, when a heart beat is detected a radio signal is transmitted, which the receiver uses to determine the current heart rate. This signal can be a simple radio pulse or a unique coded signal from the chest strap (such as Bluetooth, ANT, or other low-power radio link); the latter prevents one user's receiver from using signals from other nearby transmitters (known as cross-talk interference).

Newer versions include a microprocessor, which is continuously monitoring the EKG and calculating the heart rate, and other parameters. These may include accelerometers that can detect speed and distance, eliminating the need for foot worn devices.

There are a wide number of receiver designs, with various features. These include average heart rate over exercise period, time in a specific heart rate zone, calories burned, breathing rate, built-in speed and distance, and detailed logging that can be downloaded to a computer.

See also[edit]