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FILE - In this Monday, Feb. 29, 2016, file photo, Brett Broviak, a manager of respiratory and sleep services at IU Health North Hospital, shows off his Fitbit fitness tracker for the camera on the hospital's campus in Carmel, Ind. Wearing a stylish fitness tracker may help you keep tabs on things like how many steps you take, but the devices themselves _ even with the lure of a cash reward _ probably wonât improve your health, according to the biggest study yet done on the trendy technology. (AP Photo/AJ Mast, File) (AP Photo/AJ Mast, File)