The new wave of wireless technologies, fitness trackers, and body sensor devices can have great impact on healthcare systems and the quality of life. However, there have not been enough studies to prove the accuracy and precision of these trackers. The objective of this study was to evaluate the accuracy, precision, and overall performance of seventeen wearable devices currently available compared with direct observation of step counts and heart rate monitoring.
Each participant in this study used three accelerometers at a time, running the three corresponding applications of each tracker on an Android or iOS device simultaneously. Each participant was instructed to walk 200, 500, and 1,000 steps. Each set was repeated 40 times. Data was recorded after each trial, and the mean step count, standard deviation, accuracy, and precision were estimated for each tracker. Heart rate was measured by all trackers (if applicable), which support heart rate monitoring, and compared to a positive control, the Onyx Vantage 9590 professional clinical pulse oximeter.
The accuracy of the tested products ranged between 79.8% and 99.1%, while the coefficient of variation (precision) ranged between 4% and 17.5%. MisFit Shine showed the highest accuracy and precision (along with Qualcomm Toq), while Samsung Gear 2 showed the lowest accuracy, and Jawbone UP showed the lowest precision. However, Xiaomi Mi band showed the best package compared to its price.
The accuracy and precision of the selected fitness trackers are reasonable and can indicate the average level of activity and thus average energy expenditure.
Addressing the obesity problem worldwide is not only a focus of the pharmaceutical industry, but also the software and hardware technology industry. Nowadays, starting with simple pedometers, highly intelligent technology has been adopted [
The use of smartphones and wireless smart trackers in healthcare systems depends on recording activity and monitoring vital signs, such as calorie consumption, fitness activity, pulse, weight, heart rate, oxygen level, and sleep pattern [
The use and implementation of various sensors, such as 3D accelerometers, pedometers, and heart rate monitors, in mobile and wearable devices has enabled the successful use of such devices in health applications [
Devices such as the Apple Watch, Samsung Galaxy Gear 2, and Samsung Galaxy S5 mobile phone include embedded heart rate monitors. They measure the heart rate by using light to track the blood [
The use of smartphones, smart watches, wearable trackers, and new health applications has started a revolution in the healthcare system [
The objective of this study was to evaluate the accuracy and precision of currently available wearable devices with respect to their pedometer and heart rate monitor compared with direct observation of step counts and traditional devices for counting the heart rate [
The Apple Watch, Samsung Gear Fit, Samsung Gear 1, Samsung Gear 2, Samsung Gear S, iHealth Tracker (AM3), Pebble Steel, Pebble Watch, Qualcomm Toq, Motorola Moto 360, Garmin Vivofit, Mi Band, MisFit Shine, Jawbone Up, Nike+ Fuelband SE, Sony Smartwatch (SWR10), and FitBit Flex were purchased for the assessment of accuracy and precision (
This prospective study recruited four healthy adults aged between 22 and 36 years through direct verbal communication. Participants gave verbal informed consent to walk 200, 500, and 1,000 steps. An observer counted steps using a tally counter throughout the period from March 2014 until June 2015. This study was approved by the home institution's ethical committee board.
On the wrist, each participant wore three accelerometers at a time. In one pants pocket, each carried either an Android or iOS device simultaneously running the three corresponding applications of each tracker. Each set was repeated 40 times. Data was recorded after each trial, and the mean step count, standard deviation, accuracy, and precision were estimated for each tracker.
Heart rate was measured by all trackers (if applicable), which support heart rate monitoring, and compared to a positive control, the Onyx Vantage 9590 professional clinical pulse oximeter, which has been well validated for research, measured at the same time on the same hand wearing the tracker. Thirty readings were recorded for each tracker simultaneously.
Finally, the consistency of the synchronization of these trackers with their corresponding mobile application was tested 20 successive times. The number of successful synchronization was counted for each tracker to its corresponding application.
The accuracy and precision were calculated in each study. Accuracy refers to the closeness of measured values to the positive control in each study. The positive controls in case of step counting and heart rate measurements were the observer-counted steps using the tally counter and heart rate measurements obtained using the Onyx Vantage 9590 professional clinical pulse oximeter, respectively. Accuracy percentages were calculated based on the percent by which measurements deviated from the average. The coefficient of variability (CV%), between the repeated measurements for each tracker and user, represents the precision. All data and statistical analysis for each device was estimated using GraphPad Prism version 6.
Across all devices, 200, 500, and 1,000 step count observations were recorded for four participants. The participants were all males and had a mean age of 26.5 years (standard deviation [SD] = 12.8 years).
The Apple Watch showed accuracy of 99.1% (SD = 16.6) for 200 step counts, rising to 99.5% (SD = 25.8) for 1,000 step counts. It showed the most precise results for 1,000 steps (CV = 2.6). MisFit Shine showed competitive accuracy of 98.3% (SD = 7.2) for 200 steps, rising to 99.7% (SD = 39.8) for 1,000 steps. However, Samsung Gear 1 showed 97% accuracy (SD = 8.5) for 200 steps, declining to 94% (SD= 103.9) for 1,000 steps. Qualcomm Toq showed about 97% accuracy (SD = 6.9) but it showed the most precise result with CV% of 3.6. Qualcomm Toq maintained very precise results for 500 steps (CV = 5.2) and 1,000 steps (CV = 3.4).
The accuracy percentages of heart rate measurements (
Finally, there was no significant difference in the consistency of synchronization with the Apple iOS and Google Android devices. Within Android version 5 (Lollipop) showed the best consistency (
We found that several of the wearable fitness trackers and smart watches were relatively accurate for tracking step counts and heart rate. Generally, the data recorded were slightly different from observed step counts and heart rates, but they could deviate positively or negatively. Some devices reported step counts more than 15% than the observed count, but none exceeded 20% deviation.
Though the accuracy of a tracker is an important characteristic, it is not the only determinant of the quality of a tracker. The associated mobile application, compatibility with a variety of mobile operating systems, customization options, ease of use, efficacy of synchronization with the mobile devices, size, and external appearance affect the final appeal of a tracker to consumers. The mobile application has a major role as it is the interface for interpretation of data collected by a tracker.
In conclusion, consumers use these fitness trackers and smart watches to estimate physical activity, such as distance or calories burned based on step count and sleep monitoring. For such purposes, these trackers were found to be relatively accurate and beneficial. Increased physical activity facilitated by these devices could lead to clinical paybacks with low cost, as in case of the Xiaomi Mi Band priced at $14 [
We thank our colleagues from SmartCi center of research excellence (Virginia Tech-Middle East and North Africa [VT-MENA]) who provided insight, support and expertise that greatly assisted this study. We would also like to express our gratitude to Dr. Mustafa Y. ElNainay (Associate Professor of Computer and Systems Engineering, Alexandria University and Adjunct Professor of Electrical and Computer Engineering, Virginia Tech. University, USA) for his valuable comments and suggestions and for supplying us with some of the tested trackers. Finally, we thank Ms. Haidy Haggag, Ms. Nada Ahmed, and Eng. Esraa Mustafa for their comments that greatly improved the manuscript.
Supplementary materials can be found via
Trackers tested for accuracy, precision and validity. (A) Apple Watch, (B) Samsung Gear Fit, (C) Samsung Gear 1, (D) Samsung Gear 2, (E) Samsung Gear S, (F) iHealth Tracker (AM3), (G) Pebble Steel, (H) Pebble Watch, (I) Qualcomm Toq, (J) Motorola Moto 360, (K) Garmin Vivofit, (L) Mi Band, (M) MisFit Shine Band, (M) MisFit Shine necklace (O) Jawbone Up, (P) Nike+ Fuelband SE, (Q) Sony Smartband (SWR10), (R) Fit-Bit Flex.
Bluetooth synchronization consistency of Xiaomi Mi Band, Nike Fuelband SE, Fitbit Flex, and MisFit Shine across various devices with Google Android and Apple iOS mobile operating systems represented as number of successful synchronization trials per 20 times on each device.