If you have Microsoft Windows, the StretchClock break reminder can be pinned to your toolbar.
If StretchClock is pinned you will see an icon in your taskbar (usually at the bottom of your windows desktop)
To remove: right-click on the StretchClock toolbar icon and choose "Unpin this program from the taskbar."
Close and then reopen your Internet Explorer web browser.
This will completely remove StretchClock from your system and stop all of the exercises.