From tracking your heart rate to yelling at you to move, learn the ins and outs of your fitness watch
CALORIES
Pretty much the only reason most people buy a fitness tracker… When it comes to calories, a watch needs more than just a step count to make the calculation – that’s why you’ll often be asked for your age, gender, height and weight as well. Based on this info, an algorithm is used to calculate your daily burn. The more sensors and data the fitness tracker has, the more accurate the results will be.
HEART RATE
Ticking tock, on that ticker. This all comes down to a technique called photoplethysmography, or PPG. A unit in your watch sends light on to your wrist and tests how much red or green light it can see. The blood in the veins of your wrist absorbs green light. So when your heart beats, there’s more blood flow in your wrist, and more green light absorption. The faster it beats, the more absorption there is, and between heart beats, there’s less absorption of the green light.
ACTIVITY
Swimming, running, downward dog… It’s all tracked. Most of today’s trackers come with a three-point accelerometer (linked to sensors) to track movement in every direction, and some include a gyroscope for orientation and rotation. Then there’s the altimeter that can measure your altitude (for hiking or stairs). The more sensors your watch has, the more accurate it will be. These sensors measure the frequency, duration, intensity and patterns of your movement.
GPS
Where in the world are you? Perfect for keen hikers and avid runners, the GPS in your watch picks up signals from orbiting satellites to determine your location.
SLEEP
Counting sheep at night? Watches these days claim to not only monitor your hours of sleep, but also the quality and time spent in each sleep cycle. But how? They use accelerometers, the same sensors that track movement. If the sensor is registering very little or no movement, it is interpreted as a sleep state.
STEPS
Step it up, down or sideways. Pretty much any activity-tracking device has this nifty feature. This function also uses accelerometers, and is programmed with algorithms that recognise when you walk or run.
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