According to a study conducted in 2018, mainstream fitness trackers are generally accurate. They do a reasonable job when it comes to monitoring the distance covered, the number of steps taken, pulse rate, and sleep duration of an individual. However, accurate evaluation of calories burned or energy consumed remains challenging due to a significant margin of error ranging between 10 and 23 percent.
Research conducted by the University of Stanford School of Medicine compared seven fitness tracking devices worn on the wrist to measure calories burned. According to the findings, the most accurate device had a margin of error of 27 percent, and the least accurate was off by 93 percent.
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The good news is that the Stanford University School of Medicine invented a new device, to be worn on the leg, that can measure calories burned more accurately than other mainstream devices, such as smartwatches.
Factors affecting the accuracy of fitness trackers
The sensor types used on fitness trackers
The sensor technology that the fitness tracker is equipped with dramatically affects the accuracy of the fitness tracker device.
One study revealed that most fitness trackers come with a few different sensors. They generally include a pedometer, which is a lightweight part that measures the number of steps taken or distance covered by an individual, and an accelerometer that senses movement in three dimensions — side to side, forward and backward, and up and down.
Fitness trackers can also be fitted with photoplethysmography sensors (PPG) that use optical sensors to keep track of the heart rate.
Trackers can also come with an actigraph, a non-invasive device to keep track of body activity or movement in order to determine a person’s sleeping patterns.
Where the device is worn
Fitness trackers are worn on the wrist, upper arm, finger, earlobe, or forehead. The part of the body where the tracker is worn can also greatly influence the accuracy of the results.
Signals obtained from devices worn on the finger transmit higher wavelengths making these devices more accurate than those worn on other parts of the body. However, these devices can interfere with daily activities, which makes them less popular compared to those worn on other parts of the body, such as the wrist or upper arm.
The algorithm used in fitness-tracking devices
The algorithm used by the device plays a big part in determining how accurate the tracker actually is. Unfortunately, most companies that produce fitness-tracking devices do not reveal the algorithm used to evaluate the data being collected, making it difficult for consumers to compare devices.
Quality of components
Components such as the battery of the fitness tracker, the Bluetooth module it uses, and its storage capacity can affect their accuracy. Those made with high-quality components that have a large storage capacity, long battery life, and are Bluetooth and Wi-fi compatible tend to perform better and be more accurate.
Color of light emitting diode
A better number of heart rate monitoring devices come with a green light, while others have a red light and are often used in clinical settings.
Red light emits longer wavelengths than green light, so it infiltrates deep into the human body, making it possible to monitor blood pressure, oxygen saturation, and respiration.
Sleep tracking devices can monitor sleep duration, phases, quality of sleep, environmental factors affecting rest, and lifestyle factors such as caffeine consumption.
Unlike polysomnography tests, most sleep trackers are about 78 percent accurate without subtracting the time one takes to fall asleep.
However, polysomnography tests are recommended when tracking your sleeping habits because they monitor your breathing, oxygen, heart rate, brain waves, and body movement.
Not for calorie counting
It is recommended that people get 150 minutes of physical activity per week, but this sounds like a tall order for a majority of people. A random survey discovered that wearable electronic fitness trackers significantly increased physical activity. Most participants in this survey confessed that the wearable tracker motivated them to stay active, so wearing them can be beneficial. Just don’t rely too much on the information about how many calories you are burning and you should be fine.