There is no single factor that makes it stand out; in fact, you can get better individual characteristics from a variety of materials. It is how well it melds them all together that makes it special.
The elastic characteristics of natural gut allow it to react to the impact of the ball in such a way that it returns almost all of its energy in the form of velocity. This energy efficiency allows you to use a smooth natural swing, and yet hit harder with far more control.
Natural gut gives the impression of loading up slowly, and accelerating the ball smoothly. Players say the ball stays on the racquet longer. Some report that it “cups” the ball better. Its added power allows you to get all of the ball velocity you want out of a smooth, comfortable, natural swing. This combination of characteristics, added to natural gut’s ability to “bite” into the ball provide excellent control, are what makes it special.
Dynamic stiffness is the way a string reacts to impact. Natural gut has about the lowest dynamic stiffness which means it continues to “stretch” as the ball makes contact. This “stretch” mitigates the shock associated with impact and creates a very comfortable ball impact.
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