Rollerblading took place a long time ago. They used to only have roller skates until they thought of roller blades. Then they thought of grinding plates to put on roller blading so they could grind. Then they thought of five wheels on the boot of the roller blade and called them speed skates. Some people enter in contests and take a lot of risks to do those tricks. They could hurt themselves badly and maybe paralyze them for life. They have a chance of success, but it is quite likely that they could hurt themselves.