A GREAT LEAP FOR MANKIND : Weekend athletes who hold out hope of someday skying like Dominique Wilkins won’t jump for joy over the fact that soaring is in the genes, and not in the exercise program.

The pickup basketball game at a North Hollywood park was being played by a group of hyperkinetic teens on an unsanctioned holiday from school. One of them, a slender 17-year-old named Jerome, was being referred to as “Dominique.” Like Atlanta’s Dominique Wilkins, Jerome spends most of the game in flight. For every blocked shot and soaring rebound, he would hear his teammates shout, “Way to sky, Dominique!”

Jerome was a playground god, but deep inside, he knew that his jumping ability would never get him off the asphalt. Ever since he was a young boy, he had been practicing his vertical leap outside his house, marking his progress with chalk on a side wall. But about a year ago, he realized he had “maxed out. I’m not going any higher,” he said. “You would think the more you practice, the better you get, but it’s not happening.”

The dream of every Jerome, of course, is to become a Dominique Wilkins. But, like pitchers with 95-m.p.h. fastballs, great leapers are born, not made. “There’s no question about it,” said Walt Ker, Cal State Northridge women’s volleyball coach and a vertical-leap expert.

Vertical leap is one of the mysteries of sports. Some great athletes have it, some don’t. Although players like Wilkins are great because of leaping ability, it is not a prerequisite for sports immortality. Consider this all-time earthbound team: Kareem Abdul-Jabbar at center, Larry Bird and Paul Silas at forward, and, as the joke goes, any two white guards.

Vertical leap can show up in the most unlikely bodies. Spud Webb, a 5-7 guard with the Hawks, has a vertical leap of 42 inches, taking him far enough above the hoop to win the National Basketball Assn. slam-dunking contest last season. Philadelphia’s Charles Barkley, the 6-6, 275-pound forward nicknamed the “Round Mound of Rebound,” can raise his incredible bulk 35 inches off the ground.

Players who can pick quarters off the top of the backboard are part of basketball folklore. As far as historians can surmise, nobody has ever soared higher than Utah’s Darrell Griffith, who is listed in the Guinness Book of World Records with a world-best leap of 48 inches. But Wilkins and the now-retired David Thompson also have blasted 48 inches off the ground, although their marks haven’t become official.

Like the mythical Bigfoot, vertical leap legends abound. According to an NBA publicist, there was a sighting in a New York summer league last year. It seems that a kangaroo named “Herman the Helicopter” was faked into the air on defense and stayed up so long that his man was called for a three-second violation.

The Helicopter probably has something that Jerome lacks. Jumping genes.

“The ability to jump is genetic,” said Ker, who wrote a 43-page master’s thesis on vertical leap. Bound in red hard cover, the thesis is titled: “The Effects of Isokinetic Exercises, Jumping Exercises and Volleyball Practice on Vertical Jumping Ability in Highly Skilled Volleyball Players.” In tests, Ker concluded that intense training doesn’t significantly increase vertical leap in well-trained athletes.

“I’ve worked with more than 100 athletes in the last seven or eight years in jump training, and a two-inch improvement is a nice job,” he said. “The biggest improvement I’ve ever seen was only six inches.”

But how about normal weekend athletes? If they trained specifically for vertical leap, wouldn’t they make dramatic gains? No, Ker says, offering them little hope of reaching rarefied heights. “I’d say that 4- to 6-inch improvement would be very good for them, too. With training, the average guy could get to jump as high as 28 inches”--which is on the low end of the scale for skilled athletes.

There’s a company in Yadkinville, N.C., (pop. 4,500) that advertises the “Sky Jump” in the Sporting News, promising “fast results up to 10 inches.” The inventor of the Sky Jump is Rod Lowder, a computer programmer who claims to have increased his own vertical leap almost a foot.

“When I was in high school, I could not jump,” Lowder said. “But I started reading everything and came up with our program, which you can do in the privacy of your own home without gimmicks or pulleys.”

Lowder’s program consists of four exercises: rope jumping, step-ups, squats and calf raises. He suggests working out five days a week for 12 weeks. The typed, four-page primer also recommends “getting eight hours of sleep” and “not missing workouts because of laziness.”

Lowder would not say how many people have sent in $4 to buy the Sky Jump. “But it’s been successful,” he said. Lowder did concede that results “depended on the shape you were in. If you’re in great shape, the results won’t be as fast.”

After being read a description of the Sky Jump, Ker said it was “a bogus program,” adding: “There’s no speed work, nothing for specificity of training in jumping, no maximum-jump exercises. Working the calves is not essential. The calves are very unimportant muscles in jumping. And working out five days a week is not recommended. There should be 48 hours of rest between workouts.”

What about those sensational 10-inch results? “There’s no question you’ll see gains over a 12-week period,” Ker said. “But I’d still like to see somebody who’s actually improved 10 inches.”

Ker says that there is no miracle antigravity pill or secret formula for adding inches to your jump. Only if some professional couch-potato decided to take up jumping, Ker said, would quantum leaps be possible. “But I don’t see how’d you get a couch-potato interested in the first place,” he said.

Ker’s thesis showed that jumping is the best way to improve jumping. Gains depend on the level of intensity as well as a consistent, disciplined program. The jump training favored by Ker involves goal-setting and a system of visual rewards. A 3-by-8-inch card is suspended just at an athlete’s maximum jump. The athlete takes about 25 consecutive jumps during a workout. When he can hit the card consistently, the card is cut, providing tangible, motivating evidence of success.

All the major muscles in the legs and buttocks contribute to one’s ability to soar, but the quadriceps are the most important, and the key to above-average vertical takeoff is how quickly the knee can be accelerated from a bent position to full extension. In other words, Ker said, “How fast you pop the jump.”

The fast-twitch muscle fiber controls the leg’s ability to contract quickly. While long-distance runners need to develop slow-twitch fibers for endurance, athletes in basketball and volleyball must concentrate on their fast-twitch fibers.

Ker works his volleyball players extensively in jump training. He believes that even an improvement of a half-inch can be significant. His basketball counterpart at CSUN, Coach Pete Cassidy, hardly bothers.

“I’m more concerned with their other skills,” he said, “so jump training is not a big priority. I guess a great vertical leap is a plus for volleyball and basketball players, but there are so many other things to work on to improve someone’s ability as a basketball player.

“I guess what I’m saying is, I wouldn’t trade out vertical leap for basketball smarts and instincts. A lot of being good in basketball is timing and positioning.”

Todd Bowser, CSUN’s 6-7, 275-pound freshman center, estimates his vertical leap at less than 20 inches. But he’s an effective rebounder, Cassidy said, “because he knows how to get position. It’s not easy lifting 275 pounds off the floor.”

Bowser realizes how devastating he would be if he could magically add a foot to his vertical leap. “It would really be an asset,” he said, “but you do the best with what you got. There are other ways to get a rebound.”

Bowser has his own wonder plan for leaping higher, although he doesn’t recommend it. When he had his wisdom teeth removed, he lost 30 pounds.

“It was a lot easier for me to jump.”

VERTICAL LEAP STANDARDS IN INCHES AVERAGE ATHLETIC MALE

Age Groups 8-11 12-14 15-17 18-25 26-over Excellent 20 24 28 30 28 Poor 6 8 12 15 12

AVERAGE ATHLETIC FEMALE

Age Groups 8-11 12-14 15-17 18-25 26-over Excellent 17 21 25 27 25 Poor 3 5 9 12 9

Source: William Vincent, Ph.D., physical education professor at Cal State Northridge.