Fitness tracker

A wearable device – a fitness tracker, watch, or ring – promises to make you a more active person. But most of these promises last only as long as the gadget sits in a drawer after the second week. Most studies on the topic are also short: they give people a tracker, measure for a couple of months, and report an increase in steps. What happens after a year or two, when the novelty wears off, remained an open question. A Korean…