Body Position:
We start by standing under the pull-up rack, then jump upwards (power) towards the pull-up bar, perform the pull-up (strength) and return in a controlled (slow) fashion to the initial starting position. Can only be performed correctly with great upper-body (trunk) stability capability.
Video below shows regular pull up. For jump pull up, jump toward handle bar, perform pull up, drop down to the floor and jump up again.