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Leg Trackers Improve Accuracy

This new device is significantly more accurate than smartwatches.

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Legs of a runner for leg trackers

Smartwatches, depending on the make and manufacturer, can be off by 40% (or more!) when it comes to determining the base pace or movement from which caloric expenditure is measured, according to studies. To address this flaw, Stanford University researchers in Palo Alto, California, have developed a system of leg trackers, in contrast to those worn on the wrist, that’s more accurate at monitoring daily activity.

Another important feature: It measures energy expenditure in real time, similar to lab-grade systems that require gas masks and hookups to bulky equipment.

The new leg trackers have a cumulative error rate of 13% across activities, including walking, running, stair-climbing and cycling, in contrast with the more common 42% to 44% error rate among smartwatches. It requires two small leg sensors, a battery and a microcomputer, all of which are lightweight, portable and inexpensive.

The research team’s goals include promoting availability to help people better understand and improve their health. “We’re open-sourcing everything in the hopes that people will take it and run with it and make products that can improve the lives of the public,” said study author, Mykel J. Kochenderfer, PhD, associate professor of aeronautics and astronautics and of computer science at Stanford University.

Research findings are available in Nature Communications (2021; 12 [4312]).

See also: Wearable Heart Rate Trackers: Which Works Best?


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Shirley Archer-Eichenberger, JD, MA

Shirley Archer, JD, MA, is an internationally acknowledged integrative health and mindfulness specialist, best-selling author of 16 fitness and wellness books translated into multiple languages and sold worldwide, award-winning health journalist, contributing editor to Fitness Journal, media spokesperson, and IDEA's 2008 Fitness Instructor of the Year. She's a 25-year industry veteran and former health and fitness educator at the Stanford Prevention Research Center, who has served on multiple industry committees and co-authored trade books and manuals for ACE, ACSM and YMCA of the USA. She has appeared on TV worldwide and was a featured trainer on America's Next Top Model.

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