Heart rate measurement
The heart rate measurement of the fitness wristband is based in the majority of the models on a measurement of light reflections. Sensors of the wristband are able to emit light impulses that penetrate the skin layer. The light rays then hit the blood, which flows through tiny superficial blood vessels.
The light radiation used is completely harmless to the human body. Due to the reflection of the light, the bracelet is now able to judge whether the superficial blood vessel is filled with a lot or a little blood. Since the human heart can be understood as a pressure-suction-pump, two phases result in the body.
One in which blood is pumped into the body’s circulation and there is a little more blood in the vessels. And a second one, in which the empty heart sucks blood out of the body again and the vessels thus appear somewhat emptier. The fitness bracelet is therefore able to distinguish between the two phases based on the volume of blood in the superficial vessels and to equate each new “filling” of the blood vessels with a heartbeat.
Yes, various manufacturers already offer fitness wristbands with this function. A blood pressure measurement simply consists of measuring the pressure needed to initially and completely stop the flow of blood through the arterial vessels. For the most accurate measurement possible, the measuring device should be at heart level, since even fluctuations of a few centimeters can cause a shift in values of up to 10mmHg.
Likewise, the measuring device should also be positioned tightly on the forearm before the measurement in order to provide the most accurate values possible. All in all, there are a number of circumstances that are decisive for a good and accurate blood pressure measurement. Some of them can be influenced, but others depend on the fitness wristband.
All in all, it can be assumed that today’s wristbands are not yet able to provide as accurate a result as special blood pressure monitors can. Furthermore, the blood pressure at rest should be measured after a period of physical rest and then in a relaxed sitting position. During this time, however, a proper measuring device can also be applied. All in all, the blood pressure measuring function of fitness wristbands should therefore be critically examined and, in the opinion of the experts, is not yet fully developed to provide reliable values.
