I just started using AIR ALERT IV NOT 1,2 or 3. It says in the manuel and the video that it suggests doing in on a soft surface cush as a carpet to absoreb the shock which helps protect your knees

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Height: 5,9"
Weight: 141lbs/64kgs
Reach : 7,7"
Wing Span : 6,3"
Standing Vertical: 27 inches(last tested-May 1)
Running Vertical: 30 inches
Goal Standing Vertical: 45 inches
Goal Running Vertical: 50 inches
Position: PG, SG, SF
Program: VJB Novice Weighs + Stronglifts 5*5
Soccer-Basketball-Rugby