As much as I know about the game mechanics, the lower your fps, the slower is the game.
So if your computer is able to run it on 60 fps, the game will load 60 ingame frames in 1 second, but if you are only able to play with 30 fps, the game will only do 30 frames per second. So its slower. Its kind of a slow motion.
And the problem is either
1. Your computer is not good enough to run toribash with higher fps.
2. You've got some sort of fps cap activated.