Polyester String

Polyester strings became standard in pro tennis through the 1990s after Pete Sampras's competitors discovered they could generate heavy topspin while maintaining string-bed control. The key properties are stiffness and durability. Stiffness (low elasticity) gives a dense snap-back effect that bites the ball and produces topspin. Durability withstands the sustained friction of topspin swingers. The downsides are significant. Polyester loses tension rapidly (often 10–15% in the first 24 hours), reducing its performance properties. It also transmits substantially more shock and vibration to the elbow and shoulder than softer strings. Players with arm injuries are often advised to avoid poly or use it only as a cross string in a hybrid setup with natural gut mains. Full polyester setups are most appropriate for young, physically robust players who swing fast enough to activate the snap-back mechanism.

The stiffness of polyester is both its strength and its greatest risk. Stiff strings transmit shock more efficiently to the frame and through the handle to the arm. That property causes no problem for a 20-year-old hitting 1000 balls per week. But it can aggravate lateral epicondylitis (tennis elbow) in older recreational players who already have reduced tendon elasticity. The arm-stress problem is compounded when polyester is strung at high tension, which further increases stiffness and shock transmission. Some players develop arm issues while using full polyester at high tension. They can often resolve the problem entirely by switching to a hybrid at lower tension, without changing their technique.

Polyester string requires more disciplined maintenance than other string types because its performance window is shorter. Poly strings are durable and rarely break before 20-30 hours of play. But they lose their tension and elasticity much faster. A poly string that has been in the frame for three months is playing like a dead string. That holds regardless of how many balls it has been hit with. Freshly strung poly gives a crisp feel, good spin, and clear ball feedback. That performance deteriorates significantly by the second month, even for infrequent players. This is why string-maintenance awareness is as important as string selection. The best-chosen string played too long performs worse than an average string played fresh.