I came across an old topic on a forum I used to frequent a lot. And I saw I posted in it, back in 2002. So around when I first started training again. And like all newbies, we tend to be know it alls without the actual experience to back it all up 
The guy I was responding to was more right than wrong after all this time… 
The only reason why he didn’t gain more, was because of his high natural strength and thus starting Vertical Jump, but everything else is not far off! :o
his posts
Do you mean standing vertical leap (no running start) ? This ability has a very strong genetic component, the muscle fiber composition of your lower body has to be primarliy fast twitch fiber. How high can you jump now, and just as important how much can you squat ? I’m not certain but I do feel there is a correlation (for me personally at least) between your sqauting strength and your leaping ability. Also are you a fast natural sprinter, I feel this too is a big factor of how good of a vertical can be acheived.
In any case, a 8 inch increse in vertical is probably impossible. You should be able to put 3 or maybe even 4 inches on your vertical through lifting (esp lower body read:SQUATS), sprints, and keeping bodyfat under 10%.
But at the end of the day I beleive your vertical is limited strongly by your genes. When I first had my leaps tested at 16, i didn’t even work my legs and jumped 38".
After four years of heavy lower body work (squat and deadlift just shy of 500 now) I jumped a 41" . I’m only 5’8’ so its kinda useless but still it is cool to freak people out by being able to almost fly.
What I would do is hit the legs hard once a week. By hitting legs I don’t mean leg-press, leg-extension, leg-curl, and hack squat. These movements are completely useless in my opinion.
If you want strong legs, you squat with big weight, period. Yeah I know there are dudes out there who can jump 40" plus and don’t work legs at all, but your probably not one of them so you MUST squat.
Also practice the movement. Just like you would lfit weights, do 10 singles like grabing a basketball rim before or after your sprinting sessions. Sprinting is also great for your hamstrings, and I feel a faster sprinter is a higher leaper too.
So hit your legs hard in the gyn once per weak, and do a sprint/leaping workout twice per week and you should increase your veritcal leap, but most likely not by 8".
Gotta disagree with the explosive lifting and plyos stuff…
First explosive lifting is a great way to yourself up unless
A.) You have a good coach who actually has a clue about olympic lifts from experience (not a bfs clinic) and can teach you the exact way to do these lifts.
B.) You are a very well conditioned athlete with at least 2 years of training under your belt
Plyos are a spectularly efficient method to inflict soft tissue trauma to the lower body muscular and skeletal systems. I don’t care how some olympic athlete trains if he is already a genetic freak. If you want to jump higher, four simple and safer methods:
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Get lean, fat is dead weight, stay at least 8% bf (or lower if possible without excessive dieting).
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Build strong legs by squatting at the very least 2xbodyweight for atleast 10 reps. I found that my sprinting and leaping ability didn’t really increase fdut to leg strength until I was doing 315x20 once per week. Learn the correct form.
No box, No good-morning quasi-squat, down until top of thighs are parallel to floor and SLOWLY (without momentum) rise. “Speed squats” sound like an orthaepedic disater just waiting to happen.
Also do a little bit of sprinting as this is one the best hamstring and glute workouts in the world. 10 50’s and 5 100’s twice a week worked very well for me.
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Remember there is no such thing as carryover, jumping off boxes and injuring connective tisue is not going to make you jump higher. Practice the movement you are trying to improve, alot. Like I said find a bball hoop that is at least 10’ high and try 10 well rested shots at that er every two or three days. This gives you a visual indictor of how much progress you make.
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Stretching will increase your sprinting and leaping ability somewhat through mainly hamstring and hip range-of-motion improvements. Be careful though, becuase it can be over done, and you have to learn the exact way from an instructor not a book.
Try to find someone that is experienced with what is known as PNF stretching, this is one of the most effective and efficient methods for improving flexibility.
Hope this helps
