It was spontaneous combustion. Grant Hill, 14 and gangly, was playing pickup basketball on a patch of scrabbly asphalt in Reston, Virginia, his hometown. The seventh-grader caught the ball on the wing, drove in, issued a head fake to sweep the feet out from under his opponent, and then it was over. The tarnished steel net just hung there, clanking in the breeze, and the ball bounced unattended under the hoop. There was the six-foot-eight, 160-pound Hill, his cartoonishly outsize hands clutching the rim. He was cracking up with laughter.
"Everybody was cracking up," Hill remembers. "That was my first time. To a bunch of kids, dunking was a sign of something big."
Ten years later, Hill starts at forward for the Detroit Pistons. Though the comparison makes him uncomfortable — nay, combative — knowledgeable people consider the former Duke University history major and hoops All-American the eventual successor to Michael Jordan, in terms of both ability and likability; his Last-Nice-Guy-in-Sports persona has quickly become patented TV-commercial shtick. Hill's game, like Jordan's and Julius "Dr. J" Erving's before him, is built on neither sheer Neanderthal brutishness nor outrageous Curly Neal-style freneticism. Rather, he does it all, as they say, employing agility and quickness to work the game's many angles. He creates shots where there aren't shots, he finds passage to the hoop through seven-foot-four swaying cottonwoods, and — perhaps most impressive to the aspiring backyard athlete — he flies.
Or so it seems. Humans, of course, don't get Bernoulli-style lift from their wings — though not for lack of trying over the centuries. Nope, when you jump, you become a projectile, bound by the same laws of physics that control other projectiles, like asteroids, rockets, and even three-run homers. "Once you leave the ground," says Jeff Broker of the U.S. Olympic Training Center, a biomechanist and one of the world's foremost experts on the fundamental moves of sports, "the universe — not your brain or your muscles — is driving the bus."
According to those laws, jumpers always carve a parabola with their path — a tall and skinny one, like the St. Louis Arch, for a Tomahawk Dunk, or a low and long one for a Jonathan Edwards-style world-champion triple jump. Which effect you achieve depends on your speed and angle at takeoff. Volleyball players tend to use a two-footed jump, while Hill and his ilk employ a one-footed style — you can do the latter on the run, and engaging the second leg doesn't add much oomph anyway. Hill advises starting with plenty of foot speed, and he's right; the body can actually transform some of your horizontal momentum into height. Next — and this is usually done automatically, without your having to think about it — the legs do a little jig. The body throws its weight over to the jumping leg, then shifts it back over to the "free" leg. This double-clutch, usually detectable to an observer, is rife with neuromuscular significance. Muscles, scientists have discovered, perform better if they're loaded with weight and then unloaded just before a task. "It's called a preload contraction," says Broker. "And the effect is sort of like cocking a gun. You see it in all sports — the golf swing, the sprinter's crouch, the tennis serve." A deliberate elongation of the muscle precedes the contraction, pulling more motor units into play.
For final preparation, the arms and free leg swing forcefully both forward and upward. This windup is the body trying to jump-start its own center of gravity and send it hurtling toward the hoop. "The body has rather ingeniously figured out on its own that if one's center is already moving upward, then the legs have to do less work," says Broker.
Then the muscles of the butt, hips, legs, ankles, and feet fire in rapid order — like a pack of Black Cats let loose on the sidewalk — and the force of millions of neuromuscular explosions is ushered out through the feet and toes.
Hang time is a topic fiercely debated. Big-league jumpers seem to actually hover up there, effortlessly snagging that out-of-reach Frisbee. It doesn't happen quite that easily, says retired Colonel Douglas Kirkpatrick, a professor of astronautics at the University of Colorado. Kirkpatrick's specialty is satellites, but several years ago, at the half-serious urging of a sportswriter, he applied his knowledge about flying objects to the subject of Michael Jordan. Inserting takeoff velocity, maximum height, and time aloft into complicated equations, Kirkpatrick revealed that Jordan is indeed mortal. "And so is Grant Hill," he says. "Their speed is much greater at takeoff than that of the average athlete, and what they do in the air — moving their arms low to high, say, or spreading their legs and pulling them together again — creates an illusion." Simply put, they're playing with their center of gravity so it appears their trajectory is changing — but it's not. A high-jumper messes with gravity in this way, too. By arching her back and legs over the bar in the now-standard Fosbury Flop, the jumper shifts her center of gravity outside her body. Her center actually passes underneath the bar. Thus to the legs, it seems the bar is two or three inches lower. This may seem improbable, but it's common for objects to have their center of gravity outside them; a boomerang, for instance, houses its center in the empty space between the two prongs. When Hill goes up for a towering, two-handed jam, he arcs his back like a boomerang, and his center momentarily shifts upward. It returns to his belly when he trips the spring-lock and releases forward, rattling the backboard, the rim, and the defender's sense of well-being.
"I suppose I'm not really the kind of guy who names his dunks or celebrates while running back down the court," says Hill, deploying his trademark understatedness even as he discusses his trademark understatedness. "But there's something about dunking over an opponent — I mean, right over the top, so that you bend their arms backward into the rim — that feels really ... how to put it? Intimidating. It feels very good."
The surest ways to add spring to your step aren't options for most people. Tall people naturally get higher than short people, but it's tough to grow at will. Other unchangeable biomechanical factors like the length of your levers and the ratio of fast-twitch to slow-twitch muscle fibers (faster equals higher) are more a function of genetics than anything else. Nevertheless, here are some real-world ways to add inches to your takeoff.
Reduce your body fat. The leaner your body, the less your legs work to achieve liftoff. Also, studies show that training techniques such as weights and plyometrics work better if you're already in decent shape.
Hit the road, Jack. Running long distances detracts from jumping because it changes the muscles' elasticity. But according to some sports physiologists, moderate distances can keep the leg muscles, not to mention the postural muscles of the back, firing on all cylinders. It's a debatable point, but Hill nonetheless runs two to five miles, three times a week.
Hop to it, part one. Jump training simulates real sport activity and cuts recovery time between leaps. Stand at a volleyball net or under a basketball hoop and jump as high as possible, ten times. Repeat. Do three sets of ten, four or five times a week.
Do some heavy lifting. Hill doesn't train for jumping, but he does lift weights three times a week, which sports physiologists say is ideal for improving jumping ability. Squats and leg presses add overall leg strength and power, knee extensions focus on the quads, thigh curls work the hamstrings and glutes. Most important are calf raises, which can help to increase the force with which the ankle pushes off in the final phase of the jump.
Hop to it, part two. Sometimes called depth training, plyometrics is based on the theory that rapid stretching of a muscle just prior to its shortening results in a much stronger contraction. Stand atop a 16- to 20-inch-tall bench — no higher or you'll injure the patellar tendon in your knee. Drop off the bench, and immediately upon landing on both feet, jump straight into the air. Do four sets of ten. Repeat this exercise three to four times a week. Studies show that 12 weeks of plyometric training can add as much three hey-look-at-me inches to your vertical.
A) Arms and legs pump together during the running approach. Ground velocity gained is converted to vertical velocity — a higher jump for this southpaw high jumper — upon takeoff.
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