Hello
I am looking for a free or paid programes which locks the PC screen every hour and shows the gymnastic exercises.

Which operating system are you running? Windows 7, 8, etc.

What do you mean "Shows the gymnastic exercises?"

In Windows you can display videos and pictures on the lock screen. Videos take a bit of a hack, but the same hack will basically let you run any program during the locked screen. You can set the time between locks, however the computer must be idle for that amount of time. I imagine a clever batch file and/or scheduled tasks can make this behavior happen at more regular intervals.

Furthermore for pc/mac/android/ios there tons of programs that are tailored towards productivity. Cold Turkey and Freedom will block websites and/or programs from running at your choosing. There are also dozens of options for reminder programs.