What kind of execise do hamsters need?

They need to run free in a room maybe every 3rd day or so. Let them run around without disturbing them too much while you see that they don't chew on chords and stuff. Half an hour or a quarter will be enough. Inside the cage you can give them a running wheel or whatever it is called, but some hamsters go crazy from using it so maybe you should have it in there a limited time every day. They also like to climb around on branches and rocks and such things.