Ok Ill give you something what weve been doing a number of years, enougth people have seen it. get hold of a 9" deep crash mat or a old bed matress it wont last as long, get some form of elbow protection or heavy jumper your wearing trainers. Lay on your back on the mat hands upright elbows on the mat knees bent so your feet are on the mat. Now you start a running motion never lifting your elbows or feet no more than 4" up but driving as hard as you can into the matt and pick up speed as you do. Done propely youll last 30 secs do 6 sets with 30 secs rest, youll understand what plyometrics is all about, its a cracker.