How to trick the heart rate monitor on your fitness tracker

Disclaimer: The following information provided is for educational and experimentation purposes.

You can trick a heart rate monitor that uses optical sensor to spoof a heart rate reading. This should work on trackers that use photoplethysmography(PPG) sensors that usually have a green flashing LED on the back.

The following video presents an example of the trick using pulsating colours. A heart rate tracker is placed with the sensor facing the video and wait for it to detect a reading.

Video URL: Can You Fool A Heart Rate Monitor

Another way to mimic this is to make an alternating image of 2 colours and adjust the speed according to the heart rate you require. You can test a demontration of this with the HTML/CSS code I had made here: https://www.w3schools.com/code/tryit.asp?filename=FWOZYIEUO85Y. You may adjust the code such as the speed by changing the number in the animation element, ie. "animation-duration: 0.4s" and rerun it. Generally 0.4s should take the bpm above 120.

A very basic black and white blinking might even work as shown here.

Tested succesfully on PPG heart rate trackers from National Steps Challenge: Carereach HR and Tempo 2.

Certain static surfaces like tabletops, mats and tablecloths may even be able to trick the sensor to register heartrate.

Source: HPB National Steps Challenge (Singapore)

Other sources of info:
Photoplethysmogram
https://valencell.com/blog/2015/10/optical-heart-rate-monitoring-what-you-need-to-know/