If you look closely at 0:34, at her lower back, you can see the rear of the harness which was used to propel her. This film was originally created as a commercial for Gatorade; however, since the film was rejected and never aired, it was released, whereby Television and Radio, along with thousands on the internet fell for this realistic portrayal of the Ball Girls incredible catch. Along with the catcher starting as a righty (0:08) and ending as a lefty (0:28). Credit to Stubs26