The iOS 7 update for Apple iPhone 4 is said to be reducing the device's overall speed.
However, one can simply disable some of the features in the handset, which will help iPhone 4 users to speed up their handsets to some extent. The process can also be used for Phone 5S.
Following are the steps to speed up the handsets.
Turn off the Parallax Effect/Animations
For turning off the Parallax effects on the handsets, go to Settings > General > Accessibility > Turn On Reduce Motion.
This will stop the handset from drawing translucencies, which takes a bit of handset's processing power.
Go to Settings > General > Accessibility > Turn On Increase Contrast
Turn off Bluetooth/Wifi/Airdrop When not in Use
-Pull up the control center > Turn off Wifi > Turn off Bluetooth > Turn off Airdrop.
Disable Background App Refresh
Go to Settings > General > Background App Refresh > Turn Off.
Go to settings > iCloud > Turn off anything the user think he or she don't need in a backup.
Disable Location Services (for non-essential apps)
Stop the handset from using the GPS.
Go to Settings > Privacy > Location Services.
Turn off for all the apps that do not require the service or turn them off entirely by using the switch at the top.
Disable Automatic Updating
Stop the App Store from automatically updating apps in the background.
Go to Settings > iTunes and App Store.
Turn off Updates under Automatic Downloads.
Remove Unused Apps
Homescreen > tap and hold on an app user wants to remove, until they all start to wriggle.
Tap the small "X" in the corner of each app which needs to be removed.
[Disclaimer: The above mentioned steps are not guaranteed to work exactly as stated. International Business Times would not be responsible for any loss of data from the device while implementing the steps. For details, users can question TheUnlockr website or can see for more details here.]