Wearable devices have dominated the market in the last couple of years for fitness monitoring and other health related metrics – however the accuracy of these trackers still plays a large role in health promotion. Data that is collected by these fitness trackers could help in improving the health and wellbeing of the individuals who wear them.


Today, Annabel and the Longevity Exercise Physiology teams at Drummoyne, EdgecliffMarrickvilleBella VistaRandwick, PymbleBalmain, Neutral Bay, Coburg – Melbourne and Barrie, Ontario – Canada discuss the accuracy of smart watches and how precise they are tabulating the data that they collect including calories, step count and sleep quality.


Fitness trackers are modern digital devices that serve many purposes beyond mirroring smartphone notifications and functions. These devices are wearables that mostly come in the form of digital watches or bands that people wear on their wrists. The device tracks the wearer’s physical activity through in-built sensors that detect motion, count steps, calories, distance, sleep patterns, etc., necessary to understand the overall activity levels of each individual. There are many brands of fitness trackers available in the market such as Fitbit, Apple Watch, Garmin, Amazfit, Huawei Band, and more. According to a study published in the British Journal of Sports Medicine, fitness trackers and apps have been proven to promote physical activity among 18 to 65 year old adults without chronic illness. The study also concluded that combined with smartphone apps, fitness trackers are effective in improving physical activity levels (Bizel, Srinivasan & Zeitouny, 2022).


Fitness trackers are modern inventions, constantly reminding people to invest a portion of their time in their health and well-being. For these watches to be of benefit, it is important that the data collected is accurate and reflects real world performance. Interestingly, studies have found that the number of steps reported by difference devices worn at the same time could vary as much as 26%. Comparably, the variations in distance travelled, based on step count followed the same trend. Reporting of other health indicators including calories burned are heavily dependent on the brand of the device as well as the algorithm to calculate the data. These types of self-tracking devices have been reported to be effective for promoting and maintaining physical activity (PA) (G. Bender, C. Hoffstot, T. Combs & Hooshangi, 2017).


“Studies have found that the number of steps reported by difference devices worn at the same time could vary as much as 26%”


One study that compared fitness tracking devices, including two models of Fitbit, a Garmin smartwatch, and an Apple Watch over a 14-day period. During this study, data on the number of steps taken, distance travelled, and calories burned by each subject was collected and a comparison analysis was performed. The analysis showed that step count, miles travelled, and calories burned could vary significantly when devices of different manufacturers are compared side by side. Additionally, the variations in step count and the distance travelled followed the same trend. This study found no trend between the variation in calories burned and what was observed for the step and distance variations (Hajj-Boutros, Landry-Duval, Comtois, Gouspillou & Karelis, 2022).



Another study examined the accuracy of 3 recently released wrist-worn devices (Apple Watch 6, Polar Vantage V and Fitbit Sense) for heart rate and energy expenditure during various activities. In terms of heart rate measurement, the Apple Watch 6 displayed the highest level of accuracy of less than 5% for all 5 activities, whereas the Polar Vantage V and the Fitbit Sense presented various degrees of accuracy dependent on the activity 2.44 – 10.76%. For energy expenditure, all 3 devices displayed poor accuracy for all 5 physical activities with a variation between 14.68 – 24.85% for Apple Watch 6, 16.54 -m25.78% for Polar Vantage V and 13.44 – 29.66% for Fitbit Sense. Therefore, we can conclude that the Apple Watch 6 was the most accurate for measuring heart rate across all 5 activities, whereas variable levels of accuracy for heart rate measurement for the Polar Vantage V and the Fitbit Sense were observed depending on the activity. As for energy expenditure, all 3 devices showed poor accuracy during all activities (JAGIM et al., 2021).


“In terms of heart rate measurement, the Apple Watch 6 displayed the highest level of accuracy of less than 5% for all 5 activities”


When using these devices to accurately monitor steps, calorie output and heart rate, healthcare professionals, athletes/coaches and the general population may want to proceed with caution on the clinical utility of energy expenditure of these devices during the implementation of an exercise training or nutritional programme (Murakami et al., 2019).


If you have a smart watch and want to learn how to accurately use it alongside your exercise program, give Longevity Exercise Physiology Edgecliff, Pymble, Marrickville, Randwick, Drummoyne, Balmain, Bella Vista, and Neutral Bay a call on 1300 964 002 to book in a session today.


Written by Annabel Bergman



  1. Bender, C., C. Hoffstot, J., T. Combs, B., & Hooshangi, S. (2017). Measuring the Fitness of Fitness Trackers. The George Washington University.

Hajj-Boutros, G., Landry-Duval, M., Comtois, A., Gouspillou, G., & Karelis, A. (2022). Wrist-worn devices for the measurement of heart rate and energy expenditure: A validation study for the Apple Watch 6, Polar Vantage V and Fitbit Sense. European Journal Of Sport Science, 1-13. doi: 10.1080/17461391.2021.2023656

JAGIM, A., KOCH-GALLUP, N., CAMIC, C., KROENING, L., NOLTE, C., & SCHROEDER, C. et al. (2021). The accuracy of fitness watches for the measurement of heart rate and energy expenditure during moderate intensity exercise. The Journal Of Sports Medicine And Physical Fitness61(2). doi: 10.23736/s0022-4707.20.11151-4

Murakami, H., Kawakami, R., Nakae, S., Yamada, Y., Nakata, Y., & Ohkawara, K. et al. (2019). Accuracy of 12 Wearable Devices for Estimating Physical Activity Energy Expenditure Using a Metabolic Chamber and the Doubly Labeled Water Method: Validation Study. JMIR Mhealth And Uhealth7(8). doi: 10.2196/13938