The force synchronization functionality is used during unsuccessful synchronizations to help you force the application to sync your data and merge all data together from your app along with the website.
If you are having issues synchronizing logs from the website to app or app to website, a force synchronization will be used to force the application to sync your data, thus resolving any issues that you are experiencing sending your data from one platform to the other.
To access the force sync functionality, you will want to log into your My-JEFIT page on the website, then when on the main profile hub, you will go to the top right hand corner of the scroll, roll over your username, then click "Settings"
After clicking on this button, you will scroll to the bottom of the page until you have found the button that states "Force Synchronization"
Then after you have clicked this button, you will open up the app, click synchronize to pull all data into your app profile.