A fitness tracker is a multifunctional, wearable device that tracks the number of characteristics in your day-to-day life. It can measure your altitude, orientation, movement, steps, rotations, calories, and even sleep. In recent years they’ve become quite popular and are commonly used to track workouts, calories burned, and sleep cycles.
While it’s commonly known that most fitness trackers aren’t 100% accurate when measuring your sleep, they still measure quite a lot. So how exactly do they do it?
Actigraphy
Actigraphy is the most popular method used in fitness trackers to track sleep and steps. This method uses a combination of two devices: Gyroscopes and Accelerometers. Gyroscopes are a built-in feature on fitness trackers that measure angular velocity. In other words, they measure how fast/when your body rotates or changes orientations. Accelerometers are another key feature used in these devices. An accelerometer will detect any changes in speed or direction and uses that information to track movement and steps.
When you stop moving for a certain length of time, your fitness device will automatically assume you’re sleeping. Essentially, it estimates when you’re asleep by tracking when you’re inactive for the longest time throughout your day. However, this isn’t the only method.
Photoplethysmography
Although actigraphy is the standard tracking tool for fitness devices, many use it in combination with photoplethysmography. This method employs something called a photodetector. If you look at the underside of your fitness devices, you’ll probably notice a little red or green LED light shining against your skin. This is the work of the photodetector.
When the light is shined on the skin’s surface, some light is reflected and measured to observe your oxygen saturation, heart rate, and blood volume. Because we breathe slightly less while sleeping, our oxygen saturation is also lowered. Thus, indicating sleep. Our heart rate decreases when we’re sleeping as well. On the other hand, our blood volume largely increases while we’re asleep.
Together, these can give our fitness trackers a good estimate of when we could be sleeping. Pretty neat, right? Well, here’s the drawback.
Are They Accurate?
Now that you know the science behind it, you’re probably wondering exactly how accurate these things are. Well, there’s one obvious fault to address, which is using motion to detect when we’re asleep. I’m sure I don’t need to tell you that we aren’t always in motion throughout the day.
Many factors must be considered when it comes to our daily movement. We could be very sick for a few days and have to lay in bed for hours on end. Your fitness device would probably mistake that for sleeping, not to mention that many people suffer from sleep disorders that make it hard for them to fall asleep.
They may lay awake in bed, trying and failing to slip into bliss. However, a fitness tracker would most likely conclude you’re sleeping. As well as many other reasons we may be lounging throughout the day.
That being said, photoplethysmography isn’t completely accurate either. Many things can cause our body to have the “symptoms” of being asleep while not actually being asleep, such as decreased heart rate, oxygen levels, and higher blood volume.
So, are they accurate? They certainly can be. However, they can also be quite inaccurate, so be aware of that when you use them.
Other Options
Now, if you’re looking for the best devices to track your sleep specifically, there are other options. There are devices made particularly just for tracking sleep and sleep patterns, and they can come in all shapes and sizes. Some are wearables like watches, rings, or even earbuds. And then there are ones that go under your mattress.
Since these are focused solely on sleep, they tend to be more accurate than fitness trackers, which focus more on steps and calories.
Like fitness trackers, sleep trackers also use data such as breathing patterns, movement, and heart rate to determine sleep data. Many of them also make use of microphones and thermometers to measure sleep data as well as vibrations.
Because of these methods, sleep devices can measure your sleep stages, snoring, movement during sleep, sleep duration, and quality. They can pick up on temperatures and noises and how they affect your sleep. And some of them can even detect if you have a sleeping issue like insomnia or sleep apnea.
Benefits of Tracking Your Sleep
Whether you use a fitness or a sleeping device, both can offer benefits when tracking your sleep patterns. Many of us don’t really pay attention to our sleeping habits and we don’t realize that sleeping affects us way more than we think it does. Good or bad sleeping habits affect our daily productivity, motivation, and mood.
The less quality sleep you get, the less likely it is for you to complete all the tasks you planned for that day. The less motivated you are to make healthier decisions, the less inclined you’ll be to be active or productive.
But it’s not just about more sleep; it’s about the quality of sleep. Productive sleep. Nine hours of tossing and turning just aren’t quality sleep. Five to seven hours of truly restful sleep, in this case, would be more beneficial.
And this is exactly what the action of tracking our sleep aims to do. Improve sleep quality so we can improve our overall life quality.
Tracking your sleep can make you aware of how much sleep you get and unhealthy patterns you may have developed over time. It can tell you how deep you’re sleeping or keep track every time you wake up during the night. Not to mention it’s also super easy to do, especially if you already use a fitness tracker for fitness purposes.
Conclusion
Now you know how fitness trackers track sleep, allowing you to use this function to its full potential. As you can see, this feature can be very accurate depending on the watch you have and whether you use it correctly. We hope this has answered all the questions you had. Happy Sleeping!