Wrist-worn fitness trackers are more popular now than ever. Many people rely on them to make health decisions and use them as an idicator of their health and activity level. So what’s the deal with fitness trackers?

A recently published study looked at 7 commonly used fitness devises and concluded that they may not be as accurate in their calculations as we’d hope – some up to 93% inaccurate.

The trackers that were assessed were Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, PulseOn and the Samsung Gear S2. These devices typically tracked step count, heart rate, calories burned (metabolic rate), amount of activity, and sleep patterns.

Participants in the study wore these devices while being also being assessed with continuous telemetry and indirect calorimetry. They performed regular activities such as sitting, walking, running, and cycling.

How did these trackers fare? Bad… and good!

What were the devices bad at tracking?

Fitness trackers fared very poor at determining metabolic rate (calories burned) throughout the day. Measurements were anywhere from 27%- 93% inaccurate. Why was the range so high? Metabolic rate is determined based on a variety of factors. These factors includes age, gender, height, weight, activity level and other lifestyle indicators. It is a completely individualized calculation that can hardly be determined from a ‘one size fits all’ algorithm. It is interesting to note that the error was higher in those who are males, have a greater body mass index, darker skin tone and who were walking.

What were the devices good at?

These fitness trackers actually worked very well at measuring heart rate. Average heart rate deviated by only 5% compared to echocardiogram trackers. Cycling and running had the lowest amount of error and sitting had the highest.

Should I Still Use My Fitness Tracker?

Absolutely! They are still great indicator of other fitness measures. Just make sure that you are not taking the calorie-counts too seriously. Ensure that you are eating a healthy amount for your BMI and activity level. The Apple Watch actually fared the best overall compared to the other trackers. Fitness trackers can be great motivation to keep moving throughout the day, especially as we now know how detrimental sitting can be on our health. They can also be a great way to track your workouts. See your Naturopathic Doctor, nutritionist or other healthcare professional if you are unsure what is a healthy caloric intake and activity level for you.

In health,

Dr. Courtney Ranieri, ND

References

Shcherbina A, Mattsson CM, Waggott D, et al. Accuracy in Wrist-Worn, Sensor-Based Measurements of Heart Rate and Energy Expenditure in a Diverse Cohort. J Pers Med. 2017;7

Wallen, M.P.; Gomersall, S.R.; Keating, S.E.; Wisløff, U.; Coombes, J.S. Accuracy of Heart Rate Watches: Implications for Weight Management. PLoS ONE2016, 11, e0154420.