How Polyester Strings Generate More Spin

When it comes to tennis, polyester is among the top choices on pro tours because it offers extra spins, incredible stroke speed, and enables surgical control on long and aggressive strokes. From this, high performance polyesters became known as the “gut on steroids”. Top pros that use poly have wowed the world with “heavy balls” dropping just inside the base line and hitting once impossible drives and passing shots. Super-sized spins popular in today’s pro games has become all the rage that even experts in the fields of science and in international tennis organizations have studied the mechanics and physics of spin extensively.

It has been concluded that poly tennis strings, on average, do spawn more spins – up to 20% more than nylon and even beating natural gut by 11%. These studies are also backed by claims of tennis players, based on their own on-court experience. So how does poly tennis strings generate more spin?
Not long ago, despite the widespread claims of players that poly string sets have changed tennis, science could not find evidence that string material, tension, gauge, or texture really made a difference in spins. This was all changed with a 10,000-frame-per-second ultra-high-speed camera, used by Japanese engineer Yoshihiko Kawazoe who captured evidence that shed light to what happens during the 4-5 milliseconds when the ball makes contact with the strings, while testing a string lubricant. The same movement was observed and reported by the International Tennis Federation in its published technical studies released several years after.

The captured frames showed that with each ball-string impact, the strings moved and stretched laterally with the ball, snapping back as it left. The strings then transfer more energy to the returning ball in the tangential direction (parallel to the racket face), allowing it to generate more spins. Within these milliseconds, the ball seems to be livelier due to the movements in the string. This sliding out and snapping back into position leads the ball to generate more spins.
Other than tennis string material, spin depends on many playing factors. Primarily, it depends on the:

So what makes poly tennis strings good at generating more spins? Further studies and string property testing suggest that the key elements that act interactively to facilitate string ‘snap-back’ and spin are:

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