How Do Sport Watches Work?

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If you are looking to get a sport or fitness watch, you might be wondering how it works to keep track of everything.

The really advanced models can do many things such as tracking your steps, time spent active, heart rate, calories burned, oxygen levels in the blood, speed, distance, altitude, and even more.

So, how do sport watches work and measure all of these things so accurately?

How Do Sport Watches Work

Measuring Steps and Motion

One of the main things which sport watches do is to measure steps taken, as well as motion, or how long you are active for. Modern sport watches use sophisticated accelerometers, while older models may use pedometers.


Most modern sport watches come with something called a 3-axis accelerometer. Without getting too technical, these work by measuring the amount of acceleration due to gravity and can therefore figure out the angle at which they are tilted compared to the earth.

In simplest terms, these are devices which can detect movement, and they can detect even minute movements. This means that a sport watch can detect if you are standing still, if you are moving slowly, or running.

This data is then recorded inside of the sport watch, so you have access to all relevant info at all times. If your sport watch is synced with a smartphone, this data can then be synced onto the phone for easier viewing.

Remember that an accelerometer alone however cannot measure speed or distance, but when combined with a timing unit, can measure how long you are active for.


Older sport watches or even something like a basic step counter may not include a sophisticated 3-axis accelerometer. They may be using simple pedometers. A pedometer works by recording each time your body sways from side to side.

When you walk, each step you take forces your body to sway from one side to the other, and a pedometer records this motion, thus counting your steps.

Some pedometers on sport watches may attempt to convert the steps taken into distance traveled; however, because the watch does not know what the length of your stride is, this can be somewhat inaccurate.

Measuring Altitude

The next thing that some sport watches can do, the more advanced models, is to measure your altitude. This is something which you may not require for normal exercise.

However, if you are a serious athlete, such as a runner, cyclist, or even a mountain climber, keeping track of your altitude can be very important.

For instance, if you are training for a marathon that takes place on hilly terrain, knowing your ability to climb and descend can be crucial to your success.

Altimeters generally work by measuring barometric pressure, which is the amount of air pressure being put on a certain area.

The higher up you go, the less air pressure there is on a given surface, and an altimeter can track this quite accurately.

How Do Sport Watches Work

Measuring Speed and Distance

For the most accurate speed and distance measurements, high-quality sport watches also come with built-in GPS.

Using a series of satellites orbiting the earth, the GPS receiver in a sport watch can triangulate your position with extreme accuracy.

By taking exact measurements of your location at all times, a sport watch can then determine how far you have traveled, as well as the speed at which you are traveling.

Keep in mind that while those 3-axis accelerometers we discussed before can measure if you are moving or not, they cannot determine your location, how far you have traveled, or how fast you have moved. This is something that only a GPS enabled sport watch can do.

For people looking to improve their conditioning, their performance, and speed, a GPS sport watch is a must-have.

Measuring Heart Rate and More

The other thing which many sport watches do is measure your heart rate, and some can even measure the amount of dissolved oxygen in your blood, both of which are important factors for determining cardiovascular health and overall physical performance.

Most modern sport watches use technology called photoplethysmography. This tech uses a green light which the watch projects onto your skin.

The light that is not absorbed underneath the skin is reflected back towards the sensor.

The variations in the amount of light reflected back to the sensor tells it how fast your heart is beating.

When your heart beats and blood is flowing, the amount of the green light absorbed is much greater than in between heart beats, which is how photoplethysmography determines heart rate.

Measuring the amount of oxygen in your blood works in more or less the same way, except in this case, a red or infrared light is used, as opposed to the green light used to measure your heart rate.


As you can see, there are many things which a good sport watch can do.

The best functions include measuring your speed and distance, your motion, steps taken, altitude, heart rate, and blood oxygenation. If you are serious about increasing your athletic performance, getting a high-quality sport watch with all of the features we have discussed today is a big bonus.

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