The force-velocity relationship during muscle shortening occurs because the number of simultaneously attached crossbridges between the myofilaments inside the working muscle fibers determine the amount of force that a fiber can produce. The number of attached crossbridges at any one time is dependent upon the fiber shortening velocity, because the detachment rate of the crossbridges at the end of their working stroke is higher at faster shortening speeds.

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.
Unfortunately, I’m not the 6' 7" son of a Hall of Famer, so I had to resort to desperate devices—like Hennessy, an infamous and inexpensive cognac that, according to one of the two NBA players who recommended it to me, “will give you that Yah! That bounce. That little bit of meanness you need.” The little minibar-sized bottle that I downed 30 minutes into an intense session of dunk attempts on a sweltering day last summer, had no effect other than scorching my esophagus, giving me a headache and releasing from my pores an aura that, as my six-year-old put it that evening, “smells like medicine.”

The phrase "slam dunk" has entered popular usage in American English outside of its basketball meaning, to refer to a "sure thing": an action with a guaranteed outcome, or a similarly impressive achievement. This is related to the high probability of success for a slam dunk versus other types of shots. Additionally, to "be dunked on" is sometimes popularly used to indicate that a person has been easily embarrassed by another, in reference to the embarrassment associated with unsuccessfully trying to prevent an opponent from making a dunk. This ascension to popular usage is reminiscent of, for example, the way that the baseball-inspired phrases "step up to the plate" and "he hit it out of the park," or American football-inspired phrases such as "victory formation" or "hail Mary" have entered popular North American vernacular.
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.

Aside from squats, the exercises below are considered some of the best bodyweight plyometrics you can do to help improve the fast-twitch muscle fibers that enable you to jump higher and run faster. When it comes to vertical jump, plyometrics are a key. A review in the "British Journal of Sports Medicine" looked at 26 research studies that tested the effects of plyometrics on vertical jumps and found that plyometrics increased vertical jump by 8 percent. Another study reported that plyometrics helped professional athletes increase their vertical leap by 23 percent, improve their agility by 8 percent, their balance by 5 percent, and their time by 0.30 seconds on the 20-meter sprint.
Barry, who retired from the NBA in 2009, recalled that a few days before our sit-down he “drove out to the Clippers’ practice facility, wearing sneakers and board shorts, just to get my basketball fix in. Between games I pick up a ball and start shooting. In the back of my mind I’m thinking, You’re 42, man; can you still? So I get a rebound, do a little power dribble in the paint and, sure enough, throw it down. I put the ball down and walked out. I can still do that. That’s good.”
Single leg jumping with it's high impact forces and dependence on the elasticity of muscles and tendons works best for young athletes. With increasing age, the tendons and muscles lose their elasticity and springiness and the risk of injury gets higher and higher. That's why a lot of basketball players start to rely more and more on their two-foot jump as they get older. And the winner of the Olympic high jumping contest are almost always below 30.
When performing a vertical jump, the athlete exerts force at the low back, hip, knee, and ankle joints. The spine flexes as the athlete squats downwards, and then is extended by the spinal erectors over the course of the jump. The hip extensors (gluteus maximus, hamstrings, and adductor magnus) work to move the trunk and the thigh apart, which pushes the torso up and backwards. Meanwhile, the knee extensors (quadriceps) contract to extend the knee, and the calf muscles contract to move the shin backwards, towards the vertical.
I went through this progression, too. I went from touching the middle of the net at 12 years old, to dunking a basketball at 14 years old, to doing serious acrobatic 360-degree dunks at 17 years old. In college, my personal record for the vertical leap was 40 inches. At my peak, I was able to touch the top of the square on a regulation backboard, about 11.5 feet from the ground. Even now, in my thirties, I can dunk a basketball while standing underneath the basket—no run up required. I owe it all to the power of the vertical jump.
Then, in terms of exercises, you really need to get your whole body stronger. You need to improve your core, and obviously you need to improve your legs. So someone who is interested in jumping higher will find themselves doing a lot of squats. And I would suggest that if someone just started this, they could do a lot of squat exercises without even going to the gym or even bearing weight. You know, get up in their office cubicle and do ten squats. Three sets of ten reps of squats is a good workout.

Not so long ago, I played the worst basketball game of my life. I missed layups, turned over the ball, allowed my opponent free reign to the hoop. It was dark. As I slumped on the sidelines after the game, I realized how far I’d fallen from my prime a decade ago. Back then, I could dunk; now, at 33, I could barely curl my fingers over the rim. My game had regressed to hovering around the arc jacking threes. The last time I dunked a basketball, Michael Jordan was a Washington Wizard and people still listened to Coldplay.
The method described above is the most common and simplest way to measure one's vertical jump, but other more scientifically accurate methods have been devised. A pressure pad can be used to measure the time it takes for an athlete to complete a jump, and then using a kinematics equation (h = g × t2/8),[4] the computer can calculate his or her vertical jump based on the time in the air.