How Much Power Can You Get From Your Strings?
For players that are looking for a new string, more often than not, they are looking for something better. Better is relative in this sense and will different depending on the needs of the player. We carry over 600 different strings and one player’s definition of better may mean greater power or more spin, while another player may only focus on finding a string that lasts longer.
We’ve all seen the claims that various polyester strings claim to give you more power, and yet we also see much softer strings making the exact same claim, so which is true? In order to understand and determine the truth, we must analyze what exactly occurs during a typical stroke. A tennis ball is designed to conform to the rules of tennis, which dictate that a ball must be engineered to lose approximately 45% of its energy upon deformation. This deformation will occur twice in a typical groundstroke, once when the ball hits the court, and a second time when it contacts the racquet.
In general, a number of energy transitions occur in a single stroke. Some of these include: string stretching, string bed deflection, ball compression, frame twisting and frame flexing. If you will remember, we said that a stiffer racquet would theoretically provide greater power than a more flexible frame, but the opposite is true for strings. If we isolate just the frame flex as our variable in two racquets, the reason that the stiffer frame would provide more theoretical power is because the ball is designed to compress a set amount, and additional flex of the frame means that additional energy is being lost. This is partially due to the fact that in relative terms, the graphite frame has a slow recoil time, meaning that the ball is long gone before the racquet returns to its original conformation.
So why is it different with strings? It’s actually quite simple. By isolating just the string elongation and string bed deflection as variables, the way that we get more power is to have the lowest amount of lost energy. We know that the ball itself has a set amount of energy loss, and surprisingly, in spite of string construction, all are manufactured with similar inherent energy loss coefficients. The percentage of return for the strings is usually around 95 percent regardless of formulation or material. We know that upon contact, energy escapes in multiple forms, for example, the sound that escapes when bouncing a ball is a form of energy loss.
In order to understand how a softer string will provide additional power, we look to a classic example of energy loss and return. Think of two billiard balls, with sufficient stiffness and miniscule deformation, a large percentage of the energy from one ball travels into the other. Now consider two much softer objects, which will lose a larger percentage of their energy in the transfer process due to deformation. Now imagine a theoretical situation in which the ball and the strings are of the same stiffness. At contact, the overall energy will be equally split between the two objects, where the ball will lose nearly half of that energy while the strings lose only five percent. Using a fairly simple proportion, if you decrease the stiffness of the strings by 30 percent, a larger percentage of the total energy will go into the string (now 58.8 percent). The result is that a larger percentage of overall energy is subject to lower diminishing returns and overall more power.
So does this mean that a multifilament string will have more power than a polyester string? Yes and no. Assuming that the multifilament string is of lower stiffness than the polyester, it will have greater theoretical energy return, but remember that in our theoretical analysis, dropping the string stiffness by 30 percent, only results in an overall 3.5 percent power increase. In reality, the difference between strings are typically not this great, unless natural gut is involved, which exhibits significantly lower stiffness than any other string on the market.
When most players express an increase in power due to a change in string, it will more often be a perceived impression based on their personal performance. For example, if a long-time Luxilon user suddenly switched to a softer string, it is likely that they would experience a larger sweetspot, greater forgiveness, and less power loss on those shots hit just outside of the sweetspot. Based on an improved performance, the player would likely think that the string had more power, even though it had more to do with the natural properties of the string being better suited to that particular player.