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How Do Fitness Trackers Work – Let’s Find Out How

  • September 2, 2019

Fitness trackers are really popular these days. More and more people wear these devices on their wrist, claiming it can count their steps, monitor their heart rate, and do a lot more. But just how accurate are they? Do they work? And if they do, how? Let’s find out.

How do fitness trackers work? Fitness trackers use several tools to collect data about your body and your movements. They then combine these data with algorithms to interpret them. Each brand or manufacturer uses different technologies to gather the data and algorithm to explain them. That’s why different trackers may not give you the same numbers.

It is how fitness trackers generally work. But as a health-conscious person, you want to know more. Fitness trackers are fantastic health tools. Still, you would want to know how it works before you buy one. The rest of this article will help you with that.

How Fitness Band Works

Before, monitoring your heart rate includes wearing a chest strap. You can determine the distance you walk by counting them and again with the steps you climb. It is all manual work before when we want to track our fitness activity. Not anymore.

Today, you can get a fitness tracker to measure your fitness activities. It can measure how many steps you take to climb a stair, the distance you walk, your heart rate, even the calories you burn. They come in different styles but are commonly worn in the wrist.

Examples include Fitbit, the UP band, Nike+ FuelBand, the Basis Peak, the Misfit Shine, and more. Samsung Gear watches, and the Apple Watch may even be considered fitness trackers with their health tracking abilities. Wearable fitness monitoring is everywhere right now.

Measure Data Using Various Techs

But how do fitness trackers work? As I said before, fitness trackers use a wide range of tools to collect data about your health and fitness. Using a specific algorithm (something like a computer programming), it can interpret what the data means when it comes to your health.

In most cases, health tracking devices work by measuring your motion. The standard technology used is a 3-axis accelerometer to map movement in all directions. It is how fitness bands count your steps. On the other hand, some use a gyroscope for measuring orientation and rotation.

Others also have an altimeter for gauging altitude. Through all these built-in techs, a fitness tracker can count your steps, measure distance, and identify how tall the mountain you climbed is. Some devices also have sensors for measuring heart rate, sleep patterns, and temperature.

Through the sensors, the fitness tracker can measure variables regarding your activity. It can measure the duration, frequency, intensity, acceleration, and movement patterns of your exercise, among other things.

Interprets Data Using Algorithm

You must realize by now that fitness trackers can collect a massive amount of data. But you cannot use that data without the algorithm that interprets it. The specific algorithm depends on the model and brand of tracker you have.

But whatever kind of algorithm it is, they do one thing – they put together the measurements and statistics of workout into useful information. With that, it can tell you if you burned enough calories to lose weight or run enough distance so you can keep doing what you need to do for your health.

What Can Fitness Trackers Do?

Fitness trackers and other health monitoring devices can all count steps. Every model and brand differ both in what technology they use to track your activity as well as what they can do. Still, here are some of the functions of fitness trackers:

  • Steps – Using accelerometers, fitness trackers, and some smartwatches can measure your movement. They deliver stats such as the number of steps you take every day.
  • Distance – If your wearable activity tracker can measure steps, it should also be able to measure the distance you traveled using the same accelerometer.
  • Floors Climbed – Fitness trackers can track the number of stories you climbed using an altimeter. Besides this, your device may also provide you other elevation-related data.
  • Active Minutes – Most fitness trackers can also collect data on your total activity minutes. You can view the data about this activity on the tracker’s companion app. Besides the total minutes you were active in the day, it can also track your stationary time. Also, fitness trackers can record your hourly activity stats, send reminders when you have inactive for an extended time, and more.
  • Calories Burned – Many users of fitness trackers get the device to help them lose weight by its ability to keep tabs of the calories they burned. This option is pretty much a standard in every activity monitoring device.
  • Heart Rate – Some fitness trackers can record your heart rate. That includes your heart rate when you are mid-workout and resting beats per minute. Not all health tracking devices have this ability, though.
  • Sleep Quality and Time – Just like with heart rate, not all fitness trackers can record sleep quality and sleep time. They have sensors to monitor your movement with the data interpreted into information about the wearer’s sleep behavior for some time.
  • Workout Pace and Routes – This function is mostly available to expensive, more sophisticated fitness trackers. Using GPS, it can map your walks, runs, jogs, and other workouts along with your pace.
  • Fitness Score – Some fitness trackers can measure your fitness level in comparison to others of your age and gender. It will put you into a category, from poor to excellent, based on your score.
  • Specific Exercises – Using the tracking technologies built into the device, fitness trackers can identify what type of activity or exercise you are currently doing.

As I said, not all fitness trackers can perform the above functions. But the ability to track steps, distance, and calories burned are standard in most health tracking devices. People who realize how fitness is important in their health knows to buy the right fitness tracker. With the right tool, you’ll be able to stay on track and achieve your fitness goals.

How Fitness Band Calculate Heart Rate

As you know, measuring heart rate is one of the functions of a fitness tracker, although not all have this ability. Like others, you are probably wondering how a fitness band measures heart rate. The how differs from model to model and brand to brand.

Use of PPG

For instance, Apple is said to use photoplethysmography or PPG in their smartwatch. According to them, this technology measures heart rate by testing how much green or red light it sees when the device looks at the skin on the wrist.

It follows the concept that the blood is red by absorbing green light and reflecting red light. It means more blood flows in your wrist with each heartbeat. Similarly, it means your blood absorbs more green light with every beat and less green light in between beats.

Apple Watch can count your heart beats per minute by flashing LED lights on the skin in your wrist more than a hundred times for every second. Thus, it can measure your heart rate and use the information for various health purposes.


Another way that fitness trackers can measure heart rate is through bioimpedance. By bioimpedance, the tracker measures the body tissue’s resistance to tiny electric currents. With this, it can capture your heart rate along with a broad extent of other physiological signals.

With Apple’s use of PPG, it claims to be able to measure heart rate both while you are mid-workout and at rest. On the other hand, fitness trackers using bioimpedance seems to be only capable of measuring passive heart rate and resting heart rate.

The thing with a fitness band’s capability to measure heart rate is it cannot be accurate even in perfect circumstances. Irregular movements make it especially hard for the sensors to track and measure heart rate, which makes chest straps still the best option for accurate readings.

How Fitness Bands Measure Sleep

Fitness trackers keep tabs of your sleeping patterns through your movements using the built-in accelerometer or actigraphy. Either way, if the tracker does not detect any movement, direction, or speed, the assumption is you are asleep.

Although we often switch positions, it is a fact that we are mostly still when we are asleep than when awake. The body movement is used as an indicator of the wearer’s awake or sleep status. That is how fitness bands measure sleep.

Fitness trackers may also provide other sleep-related data such as when you are awake or asleep, when you are restless, and how long you were sleeping. It all depends on the kind of device you have. The problem, though, is this the method they use tend to be inaccurate.


Fitness trackers are becoming more and more popular, but they are a long way from being accurate health tools. They do work well in counting distance and height, but when it comes to sleep and heart rate, it will do well to make some improvements.

However, that does not mean that fitness trackers don’t help. Their real advantage is how they keep us aware and hype up our health efforts. The motivation that these tools offer can sometimes be more helpful in keeping us on track in achieving our health goals.