Study by racquet sports industry.....here are portions of it....two main points/
Spin
It is often assumed that control is linked with the ability to apply spin to the ball. If that is so, then does spin depend on string tension? Players often say “high tension strings bite into the ball giving more spin.” (“Biting” is used in common tennis parlance to mean creating more friction by increasing the space between strings for the ball to sink into; using rougher, stickier, textured, or shaped strings to “grab” the ball; using thinner strings to dig into the ball; or using higher tension to increase surface contact forces.)
Figure 1: View from behind the tennis racquet —
(left) ball just in contact with strings, and (right)
ball midway through impact.
Fortunately, the spin generated for a typical ball-racquet impact can easily be measured. This has been done at the University of Sheffield in England, and the results showed that the spin on the ball is not dependent on string tension or string type. In that testing it was concluded that all stringbeds are sufficiently “rough” to achieve maximum spin for the given shot. Therefore, even if thin, sticky, and tight strings were used in an attempt to increase stringbed “roughness,” there would be no actual increase in rebound spin.
However, the fact remains that players feel that they can achieve more spin with high-tension strings. Three possibilities arise: (1) the players are simply incorrect; (2) players feel a difference in some other impact related event like more or less dwell time, string movement, or ball travel across the racquet and incorrectly interpret that as more spin; (3) the player, not the racquet, does something differently when playing with higher tension strings that, indeed, produces more spin. So, we did more tests to find the answer.
The study compared two identical tennis racquets, one strung at 40 pounds and one strung at 70 pounds (the same tensions as in our previously mentioned spin study). The impact apparatus can be set up to simulate a player hitting a topspin groundstroke, and we can measure the ball rebound spin using a high speed video camera operating at 240 frames/sec. As in previous testing, it was found that the measured rebound spin for both racquets was identical. So have the players’ perceptions been proven wrong?
Not necessarily. Because tighter strings produce less velocity, the ball will land shorter in the court. To make up for this, the player might swing harder generating more spin. In this case, it is not tighter strings that produce more spin, but the player’s response to tighter strings. In any case, the player is likely to notice the greater spin without realizing that he is swinging faster.
Similarly, even if the player does not swing harder, he may think there is more spin with higher tensions. That is because, although the spin is not greater at higher tensions, the ball speed will be lower, so the ratio of spin to speed will be greater. The ball will then appear to land shorter in the court at slightly steeper angles and to bounce higher — in reality just consequences of less velocity.
If string tension doesn’t influence spin, it can’t influence control through spin. So we are forced to look elsewhere for our connection between string tension and control. Fortunately, we find three variables that do vary with string tension — string movement, dwell time, and ball travel across the stringbed — that might influence control.
Conclusion
Changing racquet tension does not affect spin, but it does affect string movement, dwell time, and ball contact distance. These latter parameters all can affect the ball trajectory as well as the player’s feel of the impact.
The main advice is that high string tensions make your shot more consistent and make it easier to hit topspin shots. If you do not like the “boardy” feel of high tension strings, then use a lower tension but remember to restring regularly to minimize the affects of undesirable string motion.
