A more accurate method would be to use a Jump Tester (like these here.) The problem with these, obviously, is that they are way too expensive. In fact, the only scenario in which I recommend using one of these is if you’re a coach, trainer, or athletic director who is purchasing it to test a large number of athletes over time and who needs as accurate of a number as possible for scouting purposes.
Less helpful was my early realization that I was a two-hand dunker, in light of my inability to palm a basketball on the move. It’s common knowledge among dunkers that throwing down with two hands is typically harder than with one; the former requires a higher vertical leap. So as I flailed haplessly at the rim last spring with one hand, I felt not just discouragement but also fear. Fear that I would miss big chunks of my kids’ ninth, sixth, and first years on earth just so I could come up embarrassingly short on a senseless goal that my wife and I would later estimate consumed 15 to 20 hours a week, on top of my normal work hours. And fear that I had shared this idea with my editors way too soon.
Before takeoff, or at the onset of the jump, the ball is brought to the abdomen and then the windmill motion is started by moving the ball below the waist according to the length of the player's fully extended arm. Then following the rotation of the outstretch arm, the ball is moved in a circular motion, typically moving from the front towards the back, and then slammed through the rim (from the profile view of a player facing the basket, the windmill motion most generally appears clockwise). Although, due to momentum, many players are unable to palm the ball through the entire windmill motion, the dunk is often completed with one-hand as centripetal force allows the player to guide the ball with only their dunking hand. In some instances sticky resins or powders may be applied to the palm, these are thought to improve grip and prevent loss of possession. Amongst players, subtle variations in the direction of the windmill depend on bodily orientation at takeoff and also jumping style (one-foot or two-feet) in relation to dominant hand.
My warmup on March 29, following a day of recovery, left me feeling hoppier than I’d expected, and not nearly as achy. After 10 devastating near misses, and several others that weren’t as close, Jeff lofted the best lob I would see during this journey. I leaped, controlled it with one hand and—boodaloomp—in and out. I could have wept. “You got this!” Jeff implored. “You know you got this!”
When approaching your dunk, run up with tall form and on your toes. People tend to lean forward to gain speed, this is wrong. Lean back and you will see the difference. Also when running, start off slow then gain speed into the jump. Never slow down. When you are at the poin to jump, take small strides and don't drag your foot. You want to have your front leg straight with your entire body. Again, stay leaning back some. Explode up. Keep practicing this technique. I am doing it and i went from a 32" running vert to a 38". that is how much form can do with your Dunk. (NOTE: this is for one legged jumpers)
I scoured the Internet looking for guidance. There are dozens of sites promising a path to dunking, most of them coded at the dawn of the Web. It was daunting finding one that seemed legit. I ended up paying $67 for the Jump Manual, an online program offered by Jacob Heller, a trainer with a 42-inch vertical who counts NBA players among his clients, according to his website. Next, I ordered a pair of Strength Shoes. You’ll remember these if you’re a basketball player of a certain age—the ridiculous-looking training kicks popular in the ’90s, with a platform under the toe that places your bodyweight on the balls of your feet.
If you make these few exercises a part of your basketball training, you’ll be well on your way to increasing the height of your vertical jump. Be sure to measure your jump height regularly in order to track your progress -- set goals for yourself each week and remain committed. Before long, you’ll be jumping higher and seeing noticeable improvements in your basketball game.
An important component of maximizing height in a vertical jump is attributed to the use of counter-movements of the legs and arm swings prior to take off, as both of these actions have been shown to significantly increase the body’s center of mass rise. The counter-movement of the legs, a quick bend of the knees which lowers the center of mass prior to springing upwards, has been shown to improve jump height by 12% compared to jumping without the counter-movement. This is attributed to the stretch shortening cycle of the leg muscles enabling the muscles to create more contractile energy. Furthermore, jump height can be increased another 10% by executing arm swings during the take off phase of the jump compared to if no arm swings are utilized. This involves lowering the arms distally and posteriorly during the leg counter-movements, and powerfully thrusting the arms up and over the head as the leg extension phase begins. As the arms complete the swinging movement they pull up on the lower body causing the lower musculature to contract more rapidly, hence aiding in greater jump height. Despite these increases due to technical adjustments, it appears as if optimizing both the force producing and elastic properties of the musculotendinous system in the lower limbs is largely determined by genetics and partially mutable through resistance exercise training.