Strings are the other technological variable in tennis rackets. It was once thought that stringing a racket tightly would increase power, while less tension would improve control. The opposite is actually true, though the differences are marginal: looser strings slightly increase power by turning the racket into a slingshot, while tighter strings add a bit of control by releasing the ball sooner, which lets players swing faster and brush up on the ball, creating topspin. Players routinely reinforce the myth that one type of string produces more spin than another. In the last four years, almost every top male has at some point switched from gut strings, made from cow intestines, to polyester strings—such as Luxilon—or to some combination of the two (usually polyester for the main strings, which travel from throat to tip, paired with gut on the cross strings, though Federer favors the opposite). Agassi, speaking to reporters recently, said Luxilon strings “really bite the ball,” increasing spin.
This view, however, is unfounded. “The roughness of strings, the pattern of strings, the gauge, and the materials—none of that stuff makes any noticeable difference for spin,” Lindsey said. “They probably are getting more spin, but it’s not for the reason they are saying.” Luxilon strings are stiffer than natural gut. This stiffness reduces ACOR ever so slightly, reducing power by 1 or 2 percent. Such a small decrease hardly registers on a radar gun, but it may shorten the maximum distance a ball travels by two or three feet. To compensate for that lost distance, Lindsey said, players swing harder, increasing pace and creating more spin. In essence, today’s men are responding unconsciously to less powerful string materials that, combined with larger head sizes, let them vary the speed and spin and sharpen the angles.
Taken together, this science makes sense of the sport’s evolution. Larger players of improved fitness have learned to push their rackets further—opening their stances, shortening their backswings, and swinging so forcefully that the energy they unleash lifts them off the ground. Federer and such players as Rafael Nadal, Marat Safin, and James Blake swing with such ferocity that they must use less powerful rackets in order to produce the spin and angles essential for attack. The rackets put brute force in the service of finesse. The players don’t serve-and-volley much, fearing a sharply angled, heavily spun reply. They do, however, charge the net as needed. They punish short returns. They hit dazzling—and once impossible—crosscourt winners from outside the doubles alley. The game is a lot more interesting to watch.
All of this happened with no drastic rule changes and little interference from the sport’s governing bodies. Just think if they had legislated a return to the wooden racket. The server would be striking the ball just as hard, but the returner, armed with a narrow racket that twists easily and can’t impart much topspin, would stand helplessly at the baseline. Instead of serve-and-volley, there would be serve. “The game has adapted to the circumstances we were afraid of,” Lindsey said, “and very quickly. Federer by himself is changing the whole game—back to an all-court game, only at a higher level. That’s how evolution happens.”