Activity trackers designed to count calories while exercising are popular devices. !n estimated 19 million were used in the US in 2014. A new study commissioned by the American Council on Exercise (ACE) evaluated five popular activity trackers to determine which ones delivered as advertised. The results were clear. Many of the devices tested could effectively measure steps taken when walking, running, and using an elliptical trainer within 10% accuracy; however, they were inaccurate for tracking steps for exercises involving complex movements such as sports, weight lifting or cross training. Of all the trackers tested, the Jawbone UP yielded the most accurate step count.
Monitoring the numbers of calories burned was far less accurate than step counting because the trackers evaluated provided results ranging from 13% to 60% of the true values. “Predicting caloric expenditure is a relatively complicated process,” explained ACE Chief Science Officer Cedric X. Bryant, Ph.D. He added, “There are certain assumptions that are made when developing the algorithms that translate movement activity detected by the devices into calories burned. Even devices with the best prediction equations will have some margin of error due to natural biological variability.”
The study was conducted by researchers at the University of Wisconsin, LaCrosse. They recruited 10 men and women to help evaluate the Nike+ Fuelband, Fitbit Ultra, Jawbone UP, BodyMedia FitCore, and the Adidas MiCoach. The participants wore each of the trackers while walking and running on a level treadmill, completing an elliptical workout, and performing sports-related exercises including ladder drills, free throws, and T-drills. For accuracy assessment, all activity trackers tested in the study were compared to portable metabolic analyzers worn by all participants and the NL-2000i pedometer, which has been found to be accurate by previous research studies.
However, despite the shortcomings of the devices that were evaluated, ACE recognizes that activity trackers still can serve as important tools for individuals attempting to incorporate more physical activity into their lifestyles. “Although the devices evaluated in the study aren’t ideal for measuring the number of calories burned, they can provide consumers with a reasonable estimate of how much physical activity they are incorporating into their daily routines,” explained Dr. Bryant. He added, “Having access to that information can be a valuable motivational and informational tool for people beginning a fitness journey, as well as those trying to increase their level of daily physical activity.” He added, “It is important for consumers to understand that while activity trackers may not precisely estimate caloric expenditure,” Bryant said, “they seem to accurately measure step counts during certain activities and can be used to effectively quantify and track changes in an individual’s physical-activity habits.”
The complete report can be viewed at this link.