How does a fitness bracelet measure sleep?

Do you spend most of the day sitting down and want to live a healthier lifestyle ? Then a fitness bracelet is a good investment to keep the change in place. This compact bracelet is worn like a watch. But it not only shows the time, but also other data that record your fitness level. This includes, for example, the pulse , the number of steps and the calories you burned.

In addition to this simple data, it is also possible to monitor sleep with a fitness bracelet. In the morning you will receive information about how long you slept and how the sleep phases are divided. A statement is also made about the quality of sleep .

But how are the fitness bracelets actually able to measure your sleep? Find out how such trackers work and how they record your sleep.

Various sensors must be used to record your sleep behavior . Only through the sensors and their data is it possible to get more precise information about your sleep . Which sensors are usually integrated in the fitness bands?


When we sleep, it is completely normal for us to move . You are unlikely to wake up in the same position that you fell asleep. In babies, this paralysis is practically non-existent. They move much more intensely, while adults are more in control. However, it is common to change positions several times and if you are under stress or have bad dreams, this can be reflected in the movements.

An acceleration sensor is integrated to record the movements. This measures the change in position. If you move your body, there is an acceleration on the fitness bracelet, which is recorded. The fitness bracelet records both rotations and forward or backward movement.

Such an acceleration is achieved by means of a capacitive sensor . This cnsists of two capacitor plates and a moving mass in the center. Due to the acceleration, the mass reacts with a delay and the frequency is changed via the capacitor plates. This enables the acceleration to be recorded.

Humans have a similar “sensor”. The organ of equilibrium is in the ear. The organ is filled with a liquid and hair measures the stimuli. If you turn your head in a certain direction, the liquid moves and the hair picks up this signal. If you turn over a longer period of time, the liquid does not come to rest immediately. The typical dizziness occurs.

The fitness bracelet uses the acceleration sensor to interpret your movements while you sleep. If you are particularly restless , this indicates poor sleep quality.


The heartbeat should be lower during sleep You calm down and the body finds its recovery. In order to evaluate whether this relaxation actually occurs, the fitness bracelets also measure the heart rate.

This is often done using an optical sensor. A light signal on the underside of the watch is used to examine the skin and blood flow. The sensor is able to recognize the fine color changes of the blood vessels when the heart beats and the blood pumps through the veins. The heart rate is measured based on the pulsation.

Compared to a chest strap, however, it turns out that the optical sensor is less accurate . Factors such as skin color or body hair can affect the sensor. Then he is no longer able to record the detailed color changes of the blood vessels .

The fitness bracelets are still sufficient for an approximate estimate of the heart rate . If it shows that your pulse fluctuates more or is increased during the night, this speaks for a restless night and little recovery. The more even and lower your pulse, the higher the quality of sleep is assessed.


The microphone is a sensor that records ambient noise . Most fitness trackers listen in during the night and record information about your breathing and snoring . Snoring is a significant impairment of sleep. You get less air and this disrupts regeneration.

You yourself will not always be aware that you snore or even suffer from sleep apnea. However, the microphone can be used to record exactly how often you snore and whether there are pauses in breathing. The detection of sleep apnea is not very precise and always requires checking in the sleep laboratory. But the fitness tracker can provide an indication that your breathing is less than optimal.

It is also possible to record loud ambient noises. If your pulse rises all of a sudden, noise could be responsible. Of course, you don’t notice this in your sleep. However, analyzing the fitness tracker could show that street noise , for example, has a massive impact on your sleep.


Depending on the version and price class, other sensors are also used. The sensors presented here are among the basic ones for recording your sleep behavior.

It is now up to the respective fitness tracker to interpret this data. Separate software is used for this. The information obtained can usually be used to determine exactly when you fall asleep and when a deep sleep phase occurs. This is made possible, for example, via motion detection and heart rate.

The following information is usually available to you in the morning :

Sleep duration
Duration of the deep sleep phase
Frequency of change of position
Duration of restless sleep phases
Interruptions in sleep

Based on this information, you are able to judge the quality of your sleep yourself. Especially over time, it is interesting to see whether changes in your sleep hygiene lead to an improvement in sleep. With a white noise device, you could suppress the ambient noise and sometimes sleep more peacefully. Sticking to fixed bed times and eating healthier diets can also lead to improvement.

In some cases, the software is also able to calculate a score independently . The value then shows you how high your sleep quality is. However, such a score is not very reliable and should be used with caution. It is better if you carry out the evaluation yourself and assess how tired or relaxed you feel.


If you suffer from insomnia, the fitness tracker is a suitable aid to check your sleep behavior. The fitness tracker uses several sensors to record your sleep. Based on the data obtained, an evaluation is possible and you can find out whether you are sleeping deeply and long enough.

If you want to improve your sleep, a sleep diary is useful as a companion. In this you write down which measures you have taken to improve your sleep. The next morning you write down the data from the fitness tracker and see immediately whether the measure has had an effect. In this way, your sleep behavior can be improved step by step. Use a vibration bracelet not only to record the quality of sleep, but also to be comfortably woken up in the morning.

You now know how a fitness tracker works and how the data is to be interpreted. Work continuously on your sleep hygiene and be patient so that your body gets used to this change. Then you will spend the night much more relaxed and no longer complain of fatigue.

Jamie Clark

Hello, I’m Jamie Clark, 32 years old, and I have been living in the USA for a few years.
Since I was a child, I have suffered from a house dust allergy, severely affecting me. I felt the effects both while exercising and while sleeping. Constant sneezing after getting up and difficult breathing were the consequences. The allergy has also developed into asthma, which is still a sporting restriction today.

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