This aint a huge gain in vert. but it brought me from barely touchin the rim to dunking two handed 180.
1. Take weights and put them on your shoulders and do calf raises, once every two nights. I do 50, strectch, then do another 50.
2.Sit-Ups and other stomach muscle workouts. Alot of ppl dont know this but stomach muscles play a pretty key role in vertical jump.
3.At practices etc. always jump ur highest. Try touching the rim lots, it helps.

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Lebron James, Allen Iverson, Kobe Bryant, Michael Jordan, Magic Johnson, Dwayne Wade... only forgetting one more person to be added to THAT list.... ME!