One of the reasons for the inaccuracy

[zakiyatasnim]

A fitness bracelet is not a medical device, so the heart rate is measured with an error. At rest, it is small, but just walking can be enough for the error to increase and the signal to be distorted.

The more intense the physical activity, the less accurate it is. For example, the interference caused by walking at a speed of 100 steps per minute may not be different from a pulse rate of 100 beats per minute - this will lead to an error in the calculations. And while running, the sensor is likely to not work correctly.


On the left, heart rate measurements are shown at rest, on the right, while walking.

A study that tested seven smartwatches on 60 volunteers showed:

The devices were more likely to be wrong in measuring heart malta number data rate when a person was walking — the median error reached 8.8%;
were less likely to be wrong when a person was riding a bicycle — most watches had an error of less than 5%.

Heart rate measurement result of four identical Garmin watches while walking
of heart rate measurements is the green LEDs, which are not as accurate as the red ones used in medical devices. According to Mikael Matson, a researcher at Karolinska Institutet, while red LEDs help to determine the heart rate more accurately, they do not work as well as green LEDs when moving. That is why smartwatch manufacturers install green LEDs.

In addition, the accuracy of the measurement may be affected by severe sunburn, tattoos, sweat on the skin, or a loosely tightened strap.

Step counter
An accelerometer, a device with a counterweight that responds to the body's movement in space, helps count steps and determine movement speed . It detects the acceleration of the fitness bracelet and responds to hand movements.

Some devices additionally use a gyroscope that takes into account three-dimensional movement in space, which allows:

determine how the hand moves during movement;
more accurately recognize the nature of the owner's movements.
For example, a bracelet with a gyroscope can understand that a person is running in place, doing physical exercises, or simply waving their hand vigorously.