A heart rate monitor (HRM) is a personal monitoring device that allows one to measure/display heart rate in real time or record the heart rate for later study. It is largely used to gather heart rate data while performing various types of

physical exercise Exercise is a body activity that enhances or maintains physical fitness and overall health and wellness. It is performed for various reasons, to aid growth and improve strength, develop muscles and the cardiovascular system, hone athletic ...

. Measuring electrical heart information is referred to as electrocardiography (ECG or EKG). Medical heart rate monitoring used in hospitals is usually wired and usually multiple sensors are used. Portable medical units are referred to as a Holter monitor. Consumer heart rate monitors are designed for everyday use and do not use wires to connect.

History

Early models consisted of a monitoring box with a set of electrode leads which attached to the chest. The first wireless

EKG Electrocardiography is the process of producing an electrocardiogram (ECG or EKG), a recording of the heart's electrical activity. It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the hear ...

heart rate monitor was invented in 1977 by

Polar Electro Polar Electro Oy (globally known as Polar) is a manufacturer of sports training computers, particularly known for developing the world's first wireless heart rate monitor. The company is based in Kempele, Finland and was founded in 1977. Polar h ...

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 in 1983.

Technologies

Modern heart rate monitors commonly use one of two different methods to record heart signals (electrical and optical). Both types of signals can provide the same basic heart rate data, using fully automated algorithms to measure heart rate, such as the Pan-Tompkins algorithm. ECG (

Electrocardiography Electrocardiography is the process of producing an electrocardiogram (ECG or EKG), a recording of the heart's electrical activity. It is an electrogram of the heart which is a graph of voltage versus time of the electrical activity of the hear ...

) sensors measure the bio-potential generated by electrical signals that control the expansion and contraction of heart chambers, typically implemented in medical devices. PPG (

Photoplethysmography A photoplethysmogram (PPG) is an optically obtained plethysmogram that can be used to detect blood volume changes in the microvascular bed of tissue. A PPG is often obtained by using a pulse oximeter which illuminates the skin and measures cha ...

) sensors use a light-based technology to measure the blood volume controlled by the heart's pumping action.

Electrical

The electrical monitors consist of two elements: a monitor/transmitter, which is worn on a chest strap, and a receiver. When a heartbeat is detected, a radio signal is transmitted, which the receiver uses to display/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 links). Newer technology prevents one user's receiver from using signals from other nearby transmitters (known as cross-talk interference) or eavesdropping. Note, the older

Polar Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates * Polar climate, the c ...

5.1 kHz radio transmission technology is usable underwater. Both Bluetooth and Ant+ use the 2.4 GHz radio band, which cannot send signals underwater.

Optical

More recent devices use optics to measure heart rate by shining light from an

LED A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...

through the skin and measuring how it scatters off blood vessels. In addition to measuring the heart rate, some devices using this technology are able to measure blood oxygen saturation ( SpO₂). Some recent optical sensors can also transmit data as mentioned above. Newer devices such as cell phones or watches can be used to display and/or collect the information. Some devices can simultaneously monitor heart rate, oxygen saturation, and other parameters. These may include sensors such as accelerometers, gyroscopes, and GPS to detect speed, location and distance. In recent years, it has been common for smartwatches to include heart rate monitors, which has greatly increased popularity. Some smartwatches, smart bands and cell phones often use PPG sensors.

Fitness metrics

Garmin,

, Suunto, Samsung, Google and Fitbit are vendors selling consumer heart rate products. Most companies use their own proprietary heart rate algorithms.

Accuracy

The newer, wrist based heart rate monitors have achieved almost identical levels of accuracy as their chest strap counterparts with independent tests showing up to 95% accuracy, but sometimes more than 30% error can persist for several minutes. Optical devices can be less accurate when used during vigorous activity, or when used underwater. Currently,

heart rate variability Heart rate variability (HRV) is the physiological phenomenon of variation in the time interval between heartbeats. It is measured by the variation in the beat-to-beat interval. Other terms used include: "cycle length variability", "R–R variabi ...

is less available on optical devices. Apple introduced HRV data collection to the Apple Watch devices in 2018.

References

External links

*{{Commons-inline, Heart rate monitors, Heart rate monitors
Visualization of ECG recordings using Python program ECG-pyview
A simple Python program visualizing raw data produced by chest strap based ECG sportesters. Enables to inspect ECG recordings having lengths up to days. ''(Open source, non-commercial use, use matplotlib.)
demo video
'' Biomedical engineering Diagnostic cardiology Exercise equipment Finnish inventions Medical monitoring equipment Physiological instruments