Two Fitbit models will be even more accurate when tracking users' fitness activities thanks to new updates released by Fitbit.

The Fitbit Charge HR and Surge fitness trackers will now start automatically tracking users' fitness activities with the latest updates, TechRadar reports.

Owners of the Fitbit Charge HR and Surge fitness trackers will not have to enter their own activities and exercises into the Fitbit app. A new feature called SmartTrack will notice when a user is in constant movement, detect what they are doing and then send it to the Fitbit app.

With the automatic tracking, the Fitbit app will be provided with an exercise summary, the length of the workout, calories burned and heart rate stats.

Fitbit says that SmartTrack is able to identify the various activities that users are doing. It can tell when someone is running, biking outdoors, walking, doing aerobic workouts or playing sports. Users will still be able to select their own activities, but SmartTrack will start working if they are active for 15 minutes or longer.

The next update to these two Fitbit devices is more accurate heart rate tracking during intense workouts. Fitbit uses PurePulse optical tech to constantly track heart rates. This technology has been improved so that it can be used during Exercise Mode with the Charge HR and multi-sport modes on the Surge.

The Fitbit app has been improved for all Fitbit owners. Weekly exercise goals have been added to encourage users to workout for a certain number of days per week.

The Fitbit Charge HR and the Fitbit Surge are now both offered in blue and tangerine colors. The Fitbit Charge HR also gets the new teal color.

The two updates for the Charge HR and Surge can be downloaded worldwide. The app update that includes the weekly goals are available for iOS and Windows Phones now, with Android coming soon.

The Fitbit Charge HR sells on Fitbit's website for $149.95, while the Surge sells for $249.95.