Using Activity Trackers
In this article
An activity tracker can turn a vague sense of how much you move into a record you can follow. The useful part comes when that record helps you choose a walk, notice a routine or work towards a goal. Understanding what the device measures makes those numbers easier to use.
What can your tracker tell you?
Fitness trackers are no longer just for runners or avid gym-goers. Wearable bands and watches can keep daily workout records and show patterns across weeks or months. Depending upon the make and model purchased, fitness trackers are relatively inexpensive devices. The cost and features still need to fit what you want to track.
Depending on the model, a tracker may record or estimate steps, pulse, heart-rate variability, sleep, temperature, blood oxygenation and calorie expenditure. Some watches display information from a separate glucose sensor. The FDA warned in 2024 that it had not authorized a smartwatch or smart ring to measure or estimate blood glucose independently. Check what the particular device is designed to do before relying on a reading for a health decision.
That growing volume of personal data is part of the appeal. A daily record can make a change in routine visible. A heart-rate estimate and a calorie estimate, however, can have very different levels of accuracy.
What happened when researchers added incentives?
In the 2016 TRIPPA trial, researchers recruited 800 employees in Singapore and compared four groups: no tracker, a Fitbit Zip, a tracker with charity incentives and a tracker with cash incentives. They followed physical activity and health measures at six and twelve months. This gave them a way to examine both the device and the encouragement attached to using it.
At six months, the cash and charity groups recorded more moderate-to-vigorous activity than the control group. The cash group’s advantage was no longer significant six months after the incentives stopped. At twelve months, the tracker-only and charity groups had maintained more activity than the control group. Weight, blood pressure and the other health outcomes measured did not improve at either assessment.
Activity and health are connected, but they are different outcomes to follow. The trial makes it worth asking what keeps a person moving after a reward ends, as well as what happens while the reward is offered.
Fitness tracker accuracy: what did the tests show?
A 2018 study compared the Fitbit Charge 2 and Garmin Vivosmart HR+ during daily activities and structured exercise in twenty healthy adults. Researchers checked heart rate and energy expenditure against reference measurements, including during interval training and cycling.
Errors changed with the activity and the way the watch was used. Heart-rate readings showed an overall tendency to underestimate, with larger errors during high-intensity cycling than treadmill intervals. Selecting an exercise mode mattered. Calorie estimates also differed between the devices and the reference measurements. The study tested those models under those conditions; use it to understand why a watch’s numbers deserve interpretation.
For a workout record, a repeatable pattern may be helpful even when a number is an estimate. For a medical decision, the intended use and validation of the device matter much more. Keep the distinction clear when choosing how to use your data.
Using activity trackers with a clear goal
Does this mean that fitness trackers are a waste of time and money? Clearly, they have constraints, but that does not mean they are useless. A 2017 review of fitness technology in sedentary adults discussed how professionals could combine tracking with behavior-change strategies. The device becomes part of a routine that includes goals, feedback and support.
A 2021 Johns Hopkins health article put the practical point this way: “Being more active and changing your habits is important, but it can be difficult. Tracking likely helps a lot of people when combined with a clear goal to shoot for.” Simply seeing a daily record of physical activity can be a wake-up call.
The article’s five suggestions remain straightforward: use the tracker consistently, set a goal, find activities you enjoy, recruit friends or family and be accountable. Choose a goal that fits your circumstances, then review whether the record is helping you act on it. A device on your wrist is most useful when it connects with something you actually want to do.
A wearable is one way to keep a record. Fitness apps offer another route, with their own mix of features, prompts and social support. Choose the format that fits the activity you want to follow.
Use the numbers as a guide
Consistency gives you a more complete record to compare, while the device’s measurement limits still apply. Look at patterns alongside your experience of the activity. If a watch makes your routine clearer and helps you keep moving, it can earn its place in your fitness toolbox. Choose its role with the same care you would give to any other training tool.
References
Finkelstein, E. A., Haaland, B. A., Bilger, M., Sahasranaman, A., Sloan, R. A., Nang, E. E. K., & Evenson, K. R. (2016). Effectiveness of activity trackers with and without incentives to increase physical activity (TRIPPA): a randomized controlled trial. The Lancet Diabetes & Endocrinology, 4(12), 983–995. Retrieved July 25, 2022, from https://www.thelancet.com/journals/landia/article/PIIS2213-8587(16)30284-4/fulltext
Martin, S. (2021, November 3). Could A fitness tracker boost your heart health? Johns Hopkins Medicine. Retrieved July 25, 2022, from https://www.hopkinsmedicine.org/health/wellness-and-prevention/could-a-fitness-tracker-boost-your-heart-health
Reddy, R. K., Pooni, R., Zaharieva, D. P., Senf, B., El Youssef, J., Dassau, E., Doyle, F. J. III, Clements, M. A., Rickels, M. R., Patton, S. R., Castle, J. R., Riddell, M. C., & Jacobs, P. G. (2018, December 10). Accuracy of wrist-worn activity monitors during common daily physical activities and types of structured exercise: Evaluation study. JMIR mHealth and uHealth. Retrieved July 25, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6305876/
Sullivan, A. N., & Lachman, M. E. (2017, January 11). Behavior change with fitness technology in sedentary adults: A review of the evidence for increasing physical activity. Frontiers in public health. Retrieved July 25, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5225122/
U.S. Food and Drug Administration (2024). Do Not Use Smartwatches or Smart Rings to Measure Blood Glucose Levels: FDA Safety Communication. https://www.fda.gov/medical-devices/safety-communications/do-not-use-smartwatches-or-smart-rings-measure-blood-glucose-levels-fda-safety-communication