Fitness trackers accurately measure heart rate but not calories burned

A Stanford inquiry into the accuracy of seven wristband activity monitors showed that six out of seven devices measured heart rate within 5 percent. None, however, measured energy expenditure well. Cardiology researcher Euan Ashley and his team conducted a study to determine how accurately seven types of fitness trackers measure heart rate and energy expenditure. Paul Sakuma Millions of people wear some kind of wristband activity tracker and use the device to monitor their own exercise and health, often sharing the data with their physician. But is the data accurate? Such people can take heart in knowing that if the device measures heart rate, it's probably doing a good job, a team of researchers at the Stanford University School of Medicine reports. But if it measures energy expenditure, it's probably off by a significant amount. An evaluation of seven devices in a diverse group of 60 volunteers showed that six of the devices measured heart rate with an error rate of less than 5 percent.