Wearable fitness trackers have become an ongoing trend in both the fitness and tech industry. Whether you’re at the gym or at work, you’ll see people wearing fitness trackers everywhere. But the question is, how do they actually work? How helpful are they for your workouts and are they actually worth spending hundreds of dollars on?

Fitness trackers come in all different shapes and sizes, and can be worn in different ways. They can be paired with your smartphone to use the many apps that are available to download that let further track your workouts and view your daily calorie intake. Most of them are worn on the wrist like a watch and rely on a heart rate monitor sensor that detect changes in the color of blood, which represents blood oxygenation, to calculate things like how many calories you’re burning. However, the heart rate monitors used on fitness trackers are far from perfect because there are many other factors that can affect the oxygenation of blood. The best fitness trackers do not rely on just heart rate monitors alone, but they also rely on tracking your movement. Still, fitness trackers that track your movement may not be the best way to track your workouts since it may not catch every time that you’re active.

Like we mentioned before, counting calories may actually be ineffective since we don’t exactly know how the accurate number of calories we’re consuming and burning. So for this reason alone, many people may not see the point in buying a fitness tracker. But, a fitness tracker can be a great tool to track your general daily activity and provide much more information on how you sleep. As long as you know there is a limit to what a fitness tracker can do, you may want to invest in one depending on what you are looking for.