Fitbit wearables are pretty popular among the health conscious gen users and among the largest selling brand in the health wearables space. They are marketed by the company as the ultimate devices which can help track things such as your heart rate to better improve your lifestyle. However a new study conducted by California State Polytechnic University found that they may be way off in recording heart beats. The results of study conducted by researchers at California State Polytechnic University, Pomona, in which participants’ heart rates were simultaneously measured by a Fitbit on each wrist and an echocardiogram, found that the PurePulse heart rate monitors on two Fitbit models – the Surge and Charge HR – can be off by up to 20 beats per minute. More shocking is that sometimes the two devices did not record a heart beat at all giving all the more wrong readings. Between the two devices, the researchers found a greater discrepancy with the Fitbit’s Surge compared to Charge HR. Forty three adults were put through differing levels of activity throughout a 65-minute session, from jogging to jump-roping to full-out treadmill running. Results showed that the more intense the exercise, the greater the margin of error. We’ve reached out to Fitbit for comment, and will update if we hear back.