Jason Kostrna (IMAGE)

Florida International University

Jason Kostrna

Caption

FIU researcher Jason Kostrna, associate professor of kinesiology and exercise science, wears the four smartwatches tested in his study — the Apple Watch Series 8, Fitbit Sense 2, Samsung Galaxy Watch 5 and Garmin Forerunner 955 — during a portrait session Friday, Aug. 21, 2026, at Florida International University in Miami. Kostrna led a study that found the devices overestimated calories burned during exercise, with errors increasing among participants with higher body fat percentages.

Credit

Taimy Alvarez/Florida International University

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