https://www.youtube.com/watch?v=bx_aVbBbgIA

Serious injury can result from speeds that are too high and from sheer stupidity.  Be advised.  Also, if your treadmill is backed up to a wall, you can be thrown into the wall and get serious belt burn if you get stuck while down.  This is why there are safety keys with lanyards to attach to your clothing.  If you want to prevent your children from using the treadmill and committing acts like those seen in this video, hide the safety key!