Have you ever noticed a strobing green light on the underside of your smartwatch or fitness tracker? It is this small green LED light, in combination with a light sensor, that helps measure and calculate your heart rate through a process called photoplethysmography (PPG).īecause your blood actually absorbs green light, your tracker is able to determine your heart rate by measuring the difference in light absorption at any given time. How do fitness trackers measure heart rate? The algorithms that are used to calculate the number of calories burned will vary based on the fitness tracker that you purchase, so you will want to read up on the specific device you are considering before you make your final purchase. That's why it's essential to be as detailed as possible when inputting information, such as the food that you have consumed or the activities you have participated in throughout the day. The accuracy of your fitness tracker will depend largely on the information that you manually enter into it.

The data collected by the accelerometer will be used by the algorithm when calculating the number of calories burned. Your smart watch or fitness tracker will have an accelerometer installed in it, and this will track your activity level each day. This information will be used to calculate your personal basal metabolic rate, and then that rate will be used in your device's algorithm to calculate the number of calories you are burning each day. When you first set up your fitness tracker, you will enter basic information about yourself, including your age, gender, height and weight. Here are a few factors that your fitness tracker will take into account when measuring how many calories you have burned during a specific time period: However, you may be wondering how they actually track the calories that you consume and burn each day. If you are on a mission to count calories, then a fitness tracker can be one of the most useful tools at your disposal.

How do fitness trackers measure calories burned? But, how do fitness trackers work? Our guide explores their various functions and the accuracy of these devices. These devices range from smart watches to purpose-built health trackers, and they are capable of tracking a variety of data that allows users to better understand their own habits and activities. The Fitbit provided the most accurate measure of EE when compared to the Polar Ignite watch and chest-worn device.Technology makes it easier than ever to stay healthy, but how do fitness trackers work and how accurate are the measurements they take?įitness trackers have become the go-to accessories over the last several years, and it seems that everyone is wearing some sort of smart device to help them reach their health goals and maintain healthy habits.

Despite providing a more accurate measure of HR, a chest-worn monitor does not provide a more accurate estimate of EE compared to fitness watches. For EE, MAPE values were 9.6☗.2% for the FB, 16.7☑9.6% for the PI and 13.8☑3.0% for the PTP.įitness watches relying on optical measures of HR underestimate HR compared to criterion measures during moderate intensity exercise. The MAPE values for HR were 11.6☘.7% for the FB, 11.0☑0.0% for the PI, and 6.3±5.2% for the PTP. Mean absolute percentage error (MAPE) was calculated to determine measurement error. An electrocardiogram (ECG) and indirect calorimetry were used as criterion measures for HR and EE. Twenty healthy participants (Age: 20.5☐.7 yrs., Ht: 173.4☑0.8 cm, BM: 72.8☑3.9 kg, BMI: 24.0☒.5 kg/m 2) wore two fitness watches (FB: Fitbit Versa TM, San Francisco, CA, USA and PI: Polar Ignite TM, Polar Electro Oy, Kempele, Finland) and a chest-worn HR monitor (PTP: Polar TeamPro Sensor TM, Polar Electro) during a 12-minute exercise protocol at incremental speeds. The aim of the current study was to examine the accuracy of three commercially available activity trackers in assessing heart rate (HR) and energy expenditure (EE) during moderate intensity exercise. As new technology emerges and updated fitness watches are released to the market, it is important to examine their accuracy.

Fitness calorie tracker watch