How it Works: Fitbit

How Can Such a Small Device Track Your Movement?

By Megan Tung

Fitbit Logo I have come across people who have raved about Fitbits, so I decided I wanted to discover what made them so special. I was curious about how they worked and what set a Fitbit apart from other devices including the Up and the iPhone. Is a Fitbit really worth the money? How is it able to count my steps? After doing my research I was able to answer these questions. Honestly, I am able to say that I believe a Fitbit is not worth the money because there are cheaper alternatives that are able to complete nearly the same tasks. However, I did find it interesting to learn how the Fitbit works to track movement.

What is it?

The Fitbit uses a 3-axis accelerometer that can track the number of steps taken, in addition to a few other features such as distance traveled, calories burned, and number of floors climbed. An accelerometer is an electromechanical device that measures acceleration forces. When used in the Fitbit, the accelerometer senses movement or vibrations. The more sensitive an accelerometer is, the more movement it can sense.

How Does It Work?

To be able to count the number of steps there is a finely tuned algorithm that detects unique motion patterns. The motion patterns must be large enough to meet the specific threshold of the algorithm, meaning that some steps could go uncounted if walking on very soft carpet or steps may be added if driving on a bumpy road and the algorithm's threshold is met. When one buys a Fitbit they insert their information (weight, height, gender, etc) onto the app/website, which allows for the program to generate data such as calories burned based off of the steps traveled, type and duration of exercise, and the user's personal information.

The sleep tracking aspect is very simple, it merely tracks how much you move throughout the night. This has a flaw because if you toss and turn a lot while asleep, the system could think you are awake or if you are lying still while reading, then the system could believe you are asleep.

Some of the Different Fitbit Models

All of the models have wireless syncing, are water resistant, and claim to have a long battery life. The simplest mode Fitbit offers is the "Zip", which has the ability to track steps, distance traveled, calories burned, and when you are active. The Zip has a tap display that shows your daily stats and the time. This is the most basic, meaning it the cheapest of the three models I will be discussing.

The middle model is the Fitbit Alta, which can track daily activities (number of steps, distance walked, calories burned), track sleep, has a silent alarm, has a tap display, has SmartTrack, and reminds you when to move. This model is slightly more advanced because it can recognize and record when you are exercising. In addition, there is the ability to track your sleep and has a silent alarm that vibrates to wake. Finally, the tap display can do more than the Zip; it can display smartphone notifications.

The most advanced model Fitbit currently offers is the Fitbit Surge, which comes at a steep price compared to the other models. The Surge has all the same features as the Alta but can also count how many floors climbed, track multi-sport, track heartrate, control music, and has GPS tracking. In addition, the Fitbit Surge looks very similar to the Apple Watch.
Fitbit ZipFitbit Zip

Fitbit AltaFitbit Alta
Fitbit SurgeFitbit Surge

The Future

Unless the Fitbit becomes cheaper and develops new features that are better than its competitors, the Fitbit will eventually become obsolete. The iPhone has the ability to do many of the same activities without the need for another device, in addition to being much cheaper. Yes, the actual iPhone is not cheaper, but odds are you either already own a smartphone or you are buying a smartphone for other reasons than just its ability to track movement. The iPhone alone can track steps, stairs climbed, and distance traveled through the app, Health, which comes on the iPhone. If a user was looking for more, there are free apps and much cheaper apps that provide the same features as the Fitbit models above.
Jawbone Up MoveJawbone Up Move

An app for tracking sleep is Sleep Cycle, which tracks sleep in almost the exact same way as the Fitbit. Sleep Cycle is free to download, but contains in-app purchases for more detailed data. I had a device that was very similar to the Fitbit, called the Jawbone Up Move. My Jawbone measured my steps, daily activity, calories burned, and sleep. The Jawbone is cheaper than the Fitbit Zip but can do the exact same tasks. However, I found it inconvenient to have to remember to transfer the clip every time I changed outfits, remember to put it back on after I showered, and for some of my outfits (such as dresses) it was hard to find a place for the tracker. After about a month of using the tracker I gave up and referred back to using my iPhone and Sleep Cycle because all I needed to do was carry around my phone, which I was already doing regardless of whether I wanted to track my steps.

iPhone Health AppiPhone Health App
Sleep Cycle AppSleep Cycle App (free version)

Currently, the Fitbit has the same type of systematic errors that could happen with the iPhone tracking, but the features are already developed into the iPhone so one does not have to purchase another device. Although the Fitbit does a fairly accurate job tracking movement (steps, stairs climbed, etc), it is not a perfect device due to it being possible to misjudge whether or not the person wearing the device took a step.

View More How It Works Articles

Megan Tung is a summer intern at Jameco Electronics. Megan is a rising senior at Menlo High School. Her interests include photography, music, and engineering.