Fitness trackers check physical metrics like blood oxygen level, heart rate, and whatnot. Read this article to know how does a fitness tracker work.
Dr. Yoshiro Hatano, a Japanese professor, developed the first fitness tracker in 1965. It could measure and track walking 10000 steps to fight obesity.
Since then, fitness trackers have evolved to become more advanced. Manufacturers use different technologies to track the physical metrics of its’ users.
Smartphones and fitness trackers work together. The fitness tracker on the body transfers data. Smartphones use their apps to access this data.
Most smartphone apps can fetch user data from the fitness tracker. It then shows the metrics to the users. For instance, the Fitbit platform runs on the Fitbit smartwatch. It also supports iPhone and Android phones.
How do fitness trackers track sleep?
Most fitness trackers use the built-in accelerometer. This can detect the user’s movement. It can check whether the person is asleep or awake within a given period.
In general, most of the available fitness trackers use actigraphy. Actigraphy is a method that allows measuring the gross motor activity of a person. It helps to track the rest and activity cycle.
The in-built microphone on the tracker recognizes the ambient noise of the surroundings. Low noise or silence is a sign that the person is sleeping.
Other key factors are heart rate and body temperature. The heart rate would be much lower when someone is asleep.
The room temperature also matters as people cannot sleep above 60 ℉. Thus, someone in such an environment is less likely to be sleeping.
How do fitness trackers measure heart rate?
It’s always fun looking into the smartphone screen. Especially to see the heart rate after a great workout session. I bet most of us do it!
So, how does the tracker measure our heart rate, and is it even correct? Well, there’s this technology known as PPG (photoplethysmography). Found in almost every fitness tracker manufacturers, including Apple.
Fitbit calls their technology Purepulse, although it’s based on the same tech as PPG. The secret is in the fact that our red blood reflects red and absorbs all other colors.
Under your smartwatch, you can see green lights. During heavy activities, the heart rate rises, meaning more blood flow to the veins under the skin. This results in more absorption of green light by the extra blood going there.
The trackers detect how much green light blood absorbs. This conforms to the intensity of physical activity, i.e., heart rate. On the downside, people having tattoos may not get a correct reading. This is due to blocking the path of light.
How do fitness trackers measure calories burned?
Studies show that most fitness trackers can’t measure the calories burned. Yet, they somehow give an approximate value. In general, they need some specific personal information of the users. Such as age, weight, height, gender.
These data are then combined and processed by their secret algorithm. This algorithm varies from manufacturers to trackers and apps.
At first, the users need to input the data of the metrics into the app. The app then calculates the BMR (basal metabolic rate) from these data.
If you didn’t know what BMR is, it’s the calories you burn while you rest. The BMR accounts for half the calories a person burns a whole day.
All these data help to give out an approximate if the not accurate value of calories burned.
How do fitness trackers measure blood pressure?
This particular feature is beneficial to people concerned about their health. People with heart problems must keep an eye on their blood pressure. This is because they need to detect heart conditions beforehand.
So, how reliable are these trackers in measuring blood pressure?
While at rest, the trackers can show more accurate values. But the accuracy somehow decreases during and after heavy physical activity. This is why American Heart Association urges heart patients to use a sphygmomanometer.
Most wearable fitness trackers use PPG and EKG (electrocardiogram). The former measures the heart rate while the latter tracks blood flow. The app evaluates these data with BMR and uses complex algorithms to show a result.
How can fitness trackers check blood oxygen?
Fitness trackers and smartwatches use a SpO2 tech called reflectance pulse oximetry.
The tracker emits infrared and red light. Bones and tissues underneath the skin reflect infrared and red light. The absorption of light is different in oxygen-rich blood and oxygen-deficient blood.
The difference in emitted and absorbed light helps to determine the level of oxygen in the blood.
Checking blood oxygen levels this way is not recommended over conventional clinical methods. Used by hospitals and doctors gives reliable values. These gadgets do not have medical certification for assessing patients’ diagnoses.
A value above 95% oxygen saturation level is average for healthy individuals. Anything below 92% calls for attention to find out possible health issues.
People who suffer from sleep apnea can enjoy this feature. If you haven’t known what sleep apnea is. It is a severe case where people stop breathing for short intervals during sleep. This results in snoring and uncomfortable sleep throughout the night.
How do fitness trackers calculate distance walked?
A fitness tracker uses a three-axis accelerometer to assess the movement of the user. It can detect when the person is at rest, moving, exercising, sleeping and whatnot.
While counting steps, none of the fitness trackers are precise to the point you can believe in the number! Most of the time, it undercounts or overcounts your steps.
The gyroscope that comes with fitness trackers can detect the direction of motion. The human body’s walking mechanism is such that it tilts when we put a leg forward for the next step.
Each stride has a consistent length which the app on the trackers asks you to input. The body’s tilting mechanism counts as steps. This is then multiplied by the length of the stride.
The more sophisticated algorithm in advanced trackers uses extra data. We all rely on the numbers that our fitness trackers show when we are out jogging or taking a walk from home.
But, most smartphones with GPS can track distance moved from point A to point B.
How does fitness trackers measure blood sugar level?
This particular feature is beneficial to people with diabetes. Fitness trackers with CGM (Continuous Glucose Monitor) can measure blood sugar levels.
iPhones, Androids, and Fitbit all support CGM devices. , the medical practice was to draw blood from the patients to examine blood samples. But using fitness trackers with CGM doesn’t involve such actions.
Smart trackers only detect sugar levels from subcutaneous samples. Usually, the actual sugar level in the blood takes time to reach the skin. This may not give the exact value which the users are looking for.
Big manufacturers like Novartis and Google are working and testing various prototypes. They may soon come up with a viable option for instant diabetic tests without going over to clinics.