Apple Watch Series 3 vs Apple Watch Series 4

The device is dustproof and water-resistant. Water-resistant devices can resist the penetration of water, such as powerful water jets, but not being submerged into water. Show more

Damage-resistant glass (such as Corning Gorilla Glass or Asahi Dragontrail Glass) is thin, lightweight, and can withstand high levels of force. Show more

Resistance to sweat makes it ideal for use while doing sports.

You can operate the device easily, by pressing the screen with your fingers.

The device has an electronic display to present information to the user.

The watch band is removable and can be replaced by any standard watch band of the correct size, allowing you to customise it to your liking.

A heart rate monitor can help show your fitness levels, enabling you to calculate a suitable intensity of exercise. Show more

GPS enables global positioning, useful in map, geo-tagging or navigation apps.

An accelerometer is a sensor used to measure the linear acceleration of a device. A common application is detecting when a device changes between vertical and horizontal positions.

A compass is useful in games, map and navigation software. Show more

Your blood oxygen level is a measurement how much oxygen is reaching your muscles. It is important because low levels mean that you will become easily fatigued during exercise. The more exercise you do, the better your blood oxygen levels will become.

This measures barometric air pressure. It can predict weather changes, for example a sudden drop in air pressure could mean a storm is coming. When calibrated correctly it can be used to determine altitude, which helps GPS devices to lock on quicker and with greater accuracy. Show more

It tracks how far you travel.

It tracks how many steps you take throughout the day, allowing you to see how active you have been.

Your activity data is analysed to give you reports, available to view through the app or website. This allows you to see how active you have been and to help you make improvements.

Measuring pace shows how much time it takes to travel one kilometer or one mile. For example, in running, a 4 minute kilometer would be a very good pace.

It can track your sleep, such as how long you sleep for and the quality. Show more

This is useful if you are on a strict training diet or if you are trying to lose weight. It can also help to boost your motivation.

The device syncs all of your data wirelessly, without the need for cables.

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The device can connect to Wi-Fi.

The device automatically syncs your data when in range of your computer or smartphone.

NFC (near field communication) allows a device to perform simple wireless transactions. Show more

Wi-Fi 4 (802.11n) is a wireless standard released in 2009. It has faster transfer rates and improved security compared to its predecessors – a, b, and g.

With a longer battery life, you don’t have to worry about charging the device as often.

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An indicator shows you when the device has low battery.

The battery can be recharged and used over again.

There is less chance that you will run out of battery during an adventure.

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The manufacturer offers a branded wireless charging kit. To charge the device, you simply put it down on its charging base. Show more

If you get a notification such as a call or message, the device will vibrate on your wrist or make a noise to alert you.

Vibrating alerts have a variety of uses, such as interval training.

The device has a feature that allows you to find your smartphone if you have misplaced it.

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The device can wake you using vibration, so as not to disturb anyone else sleeping in the room.

The device alerts you to incoming calls on your smartphone, and allows you extra control such as muting or rejecting the call.

It has an exercise diary, allowing you to easily keep track of your previous workouts.

Your data is synced to the cloud, making it easier to access across different devices and making sure it is always backed up in case you lose your device.

Adverts can be distracting and obtrusive. Apps and blogs without ads are more aesthetically pleasing, nicer to use, and make the content stand out.

You can download the app for free, from platforms such as Google Play or the App Store.

You can listen to your own music when working out. This can make exercising more enjoyable and motivate you to push yourself further.

The app uses your data to predict future period start dates.