WIMBLEDON, England — The tennis serve isn’t what it used to be.

The classic motion — arms down together, arms up together into a trophy pose, scratch your back with the racket, and swing — is not a thing of the past, but it’s far less common. Many of today’s players immediately bring their arms up together, quickly drop their rackets, and unload. This abbreviated swing is about as graceful as a man attacking a fly with a rolled up newspaper, but unlike tennis fans, pros care about results, not beauty. Witness a few of Andy Roddick’s 145 mph serves and one understands why young players, like 20-year-old Gaël Monfils of France, and veterans, like four-time French Open champion Justine Henin, have shortened their deliveries.

As it turns out, the abbreviated backswing doesn’t have much to do with the ever-increasing speed and spin of the modern serve, coaches and scientists say. Those who have studied the technique of Roddick and others largely have come to view it as a style choice, perhaps with minor benefits for some top players but not others.

“I don’t think there’s a real advantage, not mechanically,” a biomechanist at the University of Western Australia, Dr. Bruce Elliott, said. “It’s just a simpler movement.”

As for the rest of you hacks who want to put some more oomph behind that flutter ball, be warned: Do not do as the pros do.

“What you see is a lot of people who are trying to copy Andy’s abbreviated motion and are destroying other elements of the serve,” John Yandell, the founder of Tennisplayer. net and a coach who has performed video analysis for dozens of pros, including Henin and John McEnroe, said. “The average player is going to be much better off copying a motion like [Roger] Federer’s.”

For well above average players and pros, the abbreviated swing has potential advantages. When both arms go up together, a player more quickly arrives at the hitting position. This creates a direct path to the ball and allows for a lower and, for some, more accurate, toss.

However, it can also cause injuries if not done properly, Elliott said. Australian Patrick Rafter, whose abbreviated swing helped him win two U.S. Opens and twice reach the Wimbledon final, underwent surgery at the end of the 1999 season. Rafter used to lift his serving arm in front of him without cocking his shoulder — what folks like Elliott call “external rotation” (imagine a right-handed pitcher coiling his right side during his windup). This increased stress and caused injuries at various points in his career.

Yandell and Brian Gordon, a tennis coach enrolled in the biomechanics Ph.D. program at Indiana University, explained that the abbreviated motion perhaps simplifies the swing and toss, but it complicates the coordination of trunk rotation and leg drive that creates racket speed. When all the components come together, like on Roddick’s serve, the aces fly. If they don’t, the results are disastrous.

When Roddick first arrived on the tour, his right arm slung low, many commentators predicted that he would blow out his shoulder in a few years. Roddick’s motion looked painful. Rick Macci, who taught Roddick from age 9 to 14, knew different. He didn’t doubt Roddick could remain healthy because he had learned more traditional technique. Macci said Roddick didn’t develop the abbreviated motion until after he left Macci’s academy in Florida, while he was fooling around with some friends (they were trying to see who could hit the ball the hardest).

“He doesn’t get this power from the abbreviated backswing,” Macci said. “He’s in and out of the back scratch position faster than anybody in the world.” (Note: the “back scratch” is more of a straight drop as the hitting elbow goes up.)

Yandell has quantified this through video analysis. On his Web site, he displays side-by-side video of Roddick and Pete Sampras. In slow motion, a counter intuitive fact becomes apparent: Roddick’s abbreviated backswing forces him to have a longer, not shorter, swing than Sampras’s. When Roddick releases the ball, his right arm points to his right. He lifts the racket from there, drops it down, and then meets the ball in the same amount of time it takes Sampras to go from the upright trophy position to impact. A longer swing in the same interval equals more racket speed and a more powerful serve.

If you’re confused about why Roddick’s backswing is not the cause of this added power, look at it like this: Roddick’s shoulder, which is unusually flexible and strong, has made it possible for him to generate the speed required to meet the ball on time, despite a longer swing. The path of his swing doesn’t make his arm move faster.

“I think that some of the things that make Andy’s motion unique are unique to Andy and his phenomenal ability to move the racket that fast,” Yandell said.

If one looks around the tour, Roddick’s serve isn’t as unique as it once was, though no one has matched it for speed (he holds the tour record, set in Davis Cup, of 155 mph) or spin. To varying degrees, dozens of players, including Monfils, Henin, Rafael Nadal, Nicolas Mahut (the finalist at Queen’s Club last weekend), Richard Gasquet, Guillermo Canas, Fernando Gonzalez, and Dinara Safina have discarded the loopy, elegant service motion for a quicker burst of power. Henin’s coach, Carlos Rodriguez, has gone so far as to say that the change has prevented serious injury to Henin’s weakened shoulder (Gordon said he would be “highly surprised” if that were the case).

Ultimately, the truth doesn’t matter much. If amateurs and professionals have one thing in common, it’s that logic won’t deter them from trying something new to improve their serves, no matter how long the odds.

“Basically, it’s like anything else in sport,” Macci said. “It’s follow the leader.”

While there may be no reason to switch to the abbreviated swing, if a player is more comfortable with it, and can execute it properly, Elliott, Yandell, Gordon, and Macci agreed that there’s no reason not to do it.

“The people who it is an advantage for are those who find it easier to get into the balance position and get out very quickly,” Elliott said. “I think it has a lot to do with the body type and how you like to play the game. Roddick likes to rush things.”

If Yandell is certain of one thing, it’s that the abbreviated backswing won’t be the last biomechanical modification to the ever-evolving sport of tennis.

“The longer I’ve been in this, the more questions I have,” he said. “I think we’re just beginning to scratch the surface.”

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Andy Murray, the 20-year-old Scotsman who defeated Andy Roddick at last year’s Wimbledon, withdrew yesterday afternoon because of a lingering injury to his right wrist. Murray said he could not strike the ball properly and that doctors had advised him to skip the event rather than chance a longterm injury. His withdrawal opened a spot in the draw for 28-year-old American Kevin Kim, who will play his third Wimbledon.

tperrotta@nysun.com