How Do Fitness Trackers Work?

“Minimal Design” is driving technology today. A capable machine is not of much use until it is small enough to fit in your pocket (at least, this is what the customers expect today). Health Industry didn’t want to be left behind, which is why they introduced Fitness Trackers.

how do fitness trackers work

Fitness Trackers are simple contraptions that measure basic metrics once you strap them on. While it mostly serves as an interesting pedometer, the more advanced ones could measure your sleep patterns, pulse, and heart rate. The things that were measured by heavy machines like ECG could today be measured by a mere wristband. This does make us wonder, how do fitness trackers work?

What Are the Sensors Used in Fitness Trackers?

Fitness trackers work simply because of the range of sensors it houses inside it. The number and quality of sensors vary with every device, but the functionalities remain the same.

Here are some of the popular sensors that could be found in fitness trackers:

Sensors Used in Fitness Trackers

1. Accelerometer:

No surprises here, as this is the fundamentally most important sensor for any fitness tracker. The accelerometer is simply responsible for detecting motion. This means, whenever you move, the accelerometer registers it. Most of the fitness trackers today use a 3-axis accelerometer, which can register movement in every direction.

2. Gyroscope:

One of the newest addition to the fitness trackers is the gyroscope, which is responsible for sensing orientation and rotation.

3. Altimeter:

Even though accelerometers could sense motion in all directions, they are not particularly good with heights or upward motion. For such cases, the altimeter comes into action.

4. GPS:

Even though GPS technology is older than many of you, only the recent reduction in size enabled it to be fitted inside a fitness tracker. With so many satellites orbiting the planet, you could always be able to locate yourself on a map.

5. Bioimpedance sensor:

A bioimpedance sensor is the latest addition to the list of sensors in a fitness tracker. It checks the resistance of the skin towards very small electric changes. It measures the volume of blood flows from the impedance created and also the respiration and hydration rate with the help of electrodes.

6. Optical sensors:

These sensors work on the principle of photoplethysmography. In this process, an LED is shined through the organ in question, and the light reflected back is examined by the sensor. The optical absorption of blood is significantly higher than other body fluids; hence the sensor gets a good idea of the blood flow inside the body.

How the Sensors Add Up to Make Fitness Trackers Work?

With so many sensors with a variety of functionalities, it would be no surprise if you are still confused about how do fitness trackers work. But the thing is, the whole process is as complex as simple it is to use a fitness tracker.

To begin with, the aforementioned Accelerometer is responsible for sensing motion. Along with altimeter, it becomes possible to sense the height while climbing a mountain or a staircase. When you combine this with the gyroscope, you get every possible detail related to motion: the acceleration, frequency, intensity, and pattern of your movement. All this could be taken into account while calculating your calories burnt.

The Sleep Pattern, another important function that people look for nowadays, uses a surprising amount of guesswork. It uses a process called actigraphy, which judges your sleep from your wrist movements. This process is nowhere as accurate as polysomnography (which monitors brain activity to judge sleep), and for people whose subconscious and unconscious wrist movement are identical, this feature becomes largely useless. However, for most people, it works well enough.

Coming to more advanced functions like Heart rate and pulse, it depends upon the optical monitors like we already mentioned. The optical heart-rate monitoring technique can be similarly used to measure pulse rate, by casting light upon the veins. However, the chest trackers are more accurate than the wristbands.

Using the same sensors, one could also measure the level of oxygen and blood pressure. The idea remains the same, only the algorithm changes.

The Galvanic skin response, which is simply a cool word for the change in electrical conductivity of the skin, also adds up data for the overall result. This includes the amount of sweat you produce during an activity, which directly correlates to how your body is responding to the physical activity. This helps the corresponding application to adjust your fitness routine.

Among all this, body temperature also plays a vital role. The increase in your body temperature in response to the level of physical activity you are performing gives us vital insights. The body temperature and galvanic skin response need to match up, failure in which could be a matter of concern.

What Happens to the Data That Fitness Trackers Collect?

The data, accumulated from the variety of sensors, is never enough on its own. There needs to be a method to translate these data into meaningful results, and this comes with the help of algorithms. Algorithms are unique for every device and there is a pretty good reason for that. While designing a fitness tracker, every manufacturer has to decide upon some key points: like which error in readings to be considered, which to ignore and which must be kept without error at all costs. These individual decisions translate into the algorithms, which show you the human-understandable output on your tracker. But apart from that, the algorithms are responsible for the enormous tasks. These include correlating separate readings, raising warnings in case of a serious mismatch, combining various readings to give out a single result, etc.

For example, the count of steps alone is not enough to decide the calories burnt. The algorithms might also consider the pace and intensity of the movement, along with the body and age metrics of the individual.

Bottom Line

Fitness Trackers have a complicated process, as we have seen just now. But the amazing part is that all these complications are encapsulated in a small box, where they would never bother us. Instead, what we get is a magic device that serves as our personal doctor and keeps motivating us to stay fit and healthy.

Atul Khosla

Atul Khosla

Atul is a digital marketing professional along with a professional content writer. Writing is not only my profession but it's my passion. I will keep posting my work here from time to time. Hope you enjoy reading my articles.

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3 Responses

  1. PARTH SARTHI says:

    Very good article

  2. Sandeep Saroha says:


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