How do Fitness Trackers Work

How do Fitness Trackers Work

Fitness trackers and other wearables are considered the most important technology trend for this 2016. More and more people are changing their lifestyles into healthier ones, being more aware of the amount of exercise they do throughout the day. This is where fitness trackers enter the game. These wearables tell you useful fitness information such as the amount of steps you've done during a day, the calories you've burnt or the quality of your sleep. But how can these small wristbands tell you all this information? Read this OneHowTo article if you want to know how fitness trackers work.

What do fitness trackers have inside?

Fitness bands look very small and the majority are very thin, but on the inside they're very complex. Fitness wristbands are full of sensors that keep track of your activity. There might be some wristbands that might not include all these sensors, but the great majority nowadays do include them. These are the sensors inside fitness trackers:


These sensors are responsible for counting your steps. To do so, they measure orientation and acceleration force. They know if the device it's in horizontal or vertical position as well as if it's moving or not. There are many different types of accelerometers and each fitness tracker will have one or another. The most simple one will only have two axis, and these ones will only measure the position in two dimensions. Some others will have three axis, which will measure the position in three dimensions, therefore making it more accurate. Nowadays the majority of the fitness trackers include three-axis accelerometers.


GPS receive high-frequency, low-power radio frequency form the satellites around the earth. They measure the distance by translating the time it takes for a signal to reach your wrist. This information can lately be translated into precise coordinates. This technology still takes a lot of battery usage, but as time goes on, GPS chips will get better at managing this.

Optical heart-rate monitors

Fitness trackers don't use breast bands to measure heart rate, instead they measure it using light. Optical heart-rate monitors shine a LED through the skin and the optical sensor examines the light that shines back. Blood absorbs more light, so the differences in light level are translated into heart rate. The problem with optical heart-rate monitors nowadays is that they're not as accurate as some other forms of measurement, and sometimes the readings might not be accurate enough.

Galvanic skin response sensor

This sensor detects when someone is sweating, which gives more information to the tracker about what the user is doing. These sensors measure how much electrical connectivity the skin has. When something causes stimulation on the skin, it becomes a better conductor of electricity. If the skin is sweated, it will conduct more electricity.


Monitoring the temperature in your body is important to know whether you might be exercising too much or you're getting sick. If your temperature is rising but your hear rate isn't rising accordingly, it might be an indication that you're getting sick.

Ambient light and UV sensors

Fitness wristbands keep track of both daily activity as well as night activity and sleep. The light sensors are used for this purpose, detecting the time of the day. The light that the light sensors catch is translated into a digital signal that enters the processor inside the wristband.

UV sensors tell you when you might be absorbing UV radiation from the sun dangerous for the skin. The software compares the data gathered with the parameters that are harmful for the health and warns you to leave the sun if you're in danger of burning your skin.


These sensors are used to measure the altitude at which you find yourself. Altimeters are especially useful when going up or down the stairs, as well as for knowing the difference of altitude you've walked during the day.

How accurate are all these sensors?

Not all fitness trackers will have all the sensors listed above, however, the more sensors your fitness band has, the more accurate the information on your activity will be. It is proved that different trackers give different information about the activity, so how reliable are these bands? The sensors measure parameters such as acceleration, intensity, duration and patterns of movement, and this information is later translated into an overall reading.

For instance, when counting the calories burnt throughout the day, fitness trackers need something more than a step count. You need to include other information such as age or sex and the fitness tracker will gather all this information together with heart rate and how much you're perspiring and the number of calories burnt will come out. It might not be a perfectly accurate number but it will get very close to reality.

Although all trackers might contain the same sensors, the algorithms in each one of them are different, and so will the results. Experts agree in saying that we shouldn't put too much pressure on fitness trackers nor use them daily. Using them for one week every month will give us enough information of our overall health and fitness condition.

If you want to read similar articles to How do Fitness Trackers Work, we recommend you visit our Fitness category.