What Is a Heart Rate Monitor?

Heart Rate Monitor with Chest Strap
Heart Rate Monitor with Chest Strap. Henk Badenhorst/E+/Getty Images

A heart rate monitor is a device you wear that measures and displays your heart rate. It detects each heart beat and counts it and displays the number of beats per minute. Personal heart rate monitors are used to measure exercise intensity.

Also Known As: HRM, Polar monitor, cardio monitor

Heart rate monitors can continuously track and record heart rate during exercise, compared with an on-demand pulse monitor which only shows a value at a single point. This frees athletes from having to stop and take their pulse to determine how intense they are exercising. Many models, have indicators showing whether they are exercising in their chosen heart rate zone and give alerts when they are above or below that zone. This allows the exerciser to adjust their workout to stay at their target heart rate by slowing down or speeding up or changing incline or resistance.

Many heart rate monitors save and display the workout heart rate on a graph compared to time, speed, elevation and other aspects measured during the workout. The time in different heart rate zones may be shown at the end of the workout. Simpler heart rate monitors may only show the average heart rate for the session.

Heart Rate Monitor Design

Polar company founder Seppo Säynäjäkangas invented the wireless personal heart rate monitor in 1977 in Finland. His company was instrumental in popularizing it for athletes worldwide through the 1980's.

The wireless EKG-accurate heart rate monitor uses a strap around the chest that has electrode sensors that can detect the electrical activity of the heart as it beats. It then transmits this data to a receiver which processes and displays the signal as beats per minutes.

  • The chest strap can be made of plastic, elastic or fabric with the sensors embedded in it or attached. Sensors can be embedded in the fabric of a sports bra or shirt rather than a strap. The original sensors needed to have moist contact with the skin to get accurate readings.
  • The signal originally was sent by radiowaves to the receiver. Technology has developed to send it through ANT or Bluetooth. This enables devices such as cell phones and other mobile devices to use apps to receive the data from the heart rate monitor sensors.
  • The receiver can be a watch display, a wearable device, fitness band, mounted display for a bicycle, consoles on treadmills and other cardio machines, or mobile phone apps.

Heart Rate Zone Training with a Heart Rate Monitor

Walkers, runners, bikers use heart rate monitors to achieve the intensity of workout they want and to stay in their chosen heart rate zone. Various models have other functions such a stopwatch, time of day, pre-set workouts, calories burned.

LED Heart Rate Detection - Strapless Heart Rate Monitors

Wearable devices are being developed that use LED lights to detect blood flow and count heart rate beats per minute. Fitness bands such as the Fitbit Charge HR and smartwatches such as the Apple Watch use LED lights to read heart rate continuously during workouts, or on demand at other points of the day. Some experts say this technology is still too young to produce accurate readings, and it is the subject of a lawsuit filed in 2016 against Fitbit.

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