Posted 25th March 2023
With countless strings available on the market, choosing the most suitable string for your racket and game style can be a little overwhelming. The majority of strings are produced using similar materials and string construction types, making it very difficult to differentiate one string from another in terms of performance particularly without play testing every string on offer. To overcome this market saturation, string manufacturers will commonly advertise their strings with claims that they provide superior power and/or control, along with other performance benefits. The terminology used to endorse strings can not only be confusing and ambiguous, but can often relate to subjective performance characteristics that are not easily quantified through laboratory testing.
In this post, we’ll take a look at the common jargon that might be seen on string packaging and in product descriptions written by string manufacturers. Some of the terminology may also be seen in product reviews and is used by play testers to describe a string’s playing characteristics. This post will attempt to clarify the technical basis of each term and how it translates to performance on the court.
POWER A generic term that accounts for several string characteristics, including elasticity, gauge and tension. Elastic strings are more powerful than stiff strings; thinner gauge strings or strings at lower tension can also generate more power.
CONTROL A generic term that accounts for several string characteristics, including gauge and tension. Thinner gauge strings allow greater control, as can strings at higher tension. The perception of control is linked with the ability to apply spin to the ball and is also associated with strings that feel crisp or are more responsive.
ELASTICITY Elasticity is the string’s ability to stretch a desirable trait that corresponds to power and also makes strings feel soft. Thinner strings are generally more elastic than thicker strings of the same material. Other factors that influence elasticity are string material, construction and tension.
STIFFNESS The stiffness of a string is its ability to resist stretch. Strings with low elasticity therefore have greater stiffness. Stiff strings include those made from polyester and Kevlar, while multifilaments, synthetic gut and natural gut are all considered soft strings. Some polyester strings are softer than others, often as a result of blending polyester with other softer polymers, which has led to differentiation between stiff polyesters and soft polyesters. Perhaps confusingly, stiffness is also related to tension strings at high tension behave stiffer than the same strings at a lower tension.
COMFORT Comfort is related to the shock absorption properties of the string. Shock and vibrations caused by striking the ball are harmful to soft tissues and can lead to ailments such as tennis elbow. Stiff strings (e.g. polyester) transmit more vibration to the hand, while elastic strings made from more flexible materials are softer and more arm-friendly so provide more comfort. Comfort is also improved by using a lower string tension.
PLAYABILITY – As strings are used and worn out, they lose their desirable characteristics as tension, elasticity and resilience are lost. Playability describes how long a string remains good that is, how long a string performs near its peak performance level. A string with good playability performs well for a longer period of time. Playability can depend greatly on the string material.
STRENGTH / DURABILITY Strength and durability are both related to a string’s ability to resist breakage. Strength is defined as a string’s resistance to breakage from pulling along its length otherwise known as shear breakage, caused when the tensile strength of the string is exceeded. Kevlar strings, for example, have exceptional strength. Durability, although often used as generic term for how long a string can be expected to last, is a string’s abrasion resistance (i.e. its ability to resist wear caused by friction between the strings) and largely depends on the string construction.
SPIN / SPIN POTENTIAL Spin on the ball is not dependent on string tension, gauge, shape, texture or pattern. All stringbeds are sufficiently rough to achieve the maximum spin possible on any particular shot. This has been shown through lab testing at Sheffield Hallam University.1 Technique (swing path, angle of the racket head and racket head speed) is far more influential in generating spin. However, there is some credibility to the concept of bite and studies have also shown that polyester strings have slightly better spin potential compared with other materials due to the snap-back effect.
Spin potential can be defined as the ratio of the ball-to-string coefficient of friction divided by the string-to-string coefficient of friction. A higher ratio indicates a greater spin potential. If the string-to-string friction is low, the snap-back effect is enhanced as the main strings can slide more easily along the crosses. If the string-to-ball friction is high, this will also increase spin potential as the strings will grab the ball during the snap-back. Tennis Warehouse University, created by renowned physicist Crawford Lindsey, has a useful spin potential tool comparing a number of tennis strings on the market.
BITE String bite is a phenomenon created by friction between the ball and strings. Bite gives players better control over ball placement, better feel and more spin. Bite can be created in several ways thin strings, for example, present less surface area and penetrate the surface of the ball deeper on impact (they dig into the ball). Rougher, textured or shaped strings also grip or grab the ball. Higher tension and open string patterns, which increase the space between strings for the ball to sink into, can also improve string bite.
FEEL Feel, also referred to as touch, is one of the more subjective string performance descriptors, but typically relates to the vibrational signals that hitting the ball sends to the player. From these signals, the player develops an understanding of how they are hitting the ball, i.e. the quality and behaviour of the shot in other words, they feel dialled in to their shots. If strings have feel, this typically means that they provide good vibrational response/feedback (so are therefore responsive), but may also have a longer dwell time (pocketing the ball) and more bite than strings without feel. However, as feel is so subjective, players may use a variety of other words to more accurately describe how the strings feel:
CRISP Used to describe the feeling of new strings. A crisp feel is associated with a firm string bed with stiffer strings, resulting in shorter dwell time and more control.
MUSHY / SOGGY The opposite of crisp. Strings become mushy when they lose elasticity and become too soft, as a result of having lost too much tension. The mushy feeling masks the feel of the ball.
LIVELY Similar to crisp, in that it describes a feeling associated with new strings, but relates more to the pop or trampoline effect of strings at lower tension.
DEAD Old strings are often described as going dead. Dead strings have reduced power as a result of lost elasticity. Softer strings like multifilaments and synthetic gut may also feel mushy while polyester strings lose pop and snap-back abilities and can feel boardy.
RESPONSIVE Responsiveness is related to vibrational feedback. Vibrations caused by striking the ball carry information such as the position of the ball on the strings particularly important for touch shots like volleys and drop shots. If strings are described as having good feel it generally means they are responsive.
MUTED / DAMPENED The opposite of responsive. A muted feel reduces vibrational feedback and may be caused by over dampening of the strings. Too much dampening can make the strings feel dead.
SOFT If a string feels soft, it absorbs the force of impact with the ball, reducing shock on the player’s arm. Soft string materials have low dynamic stiffness.
BOARDY Used to describe strings at high tension or the feeling when the ball is hit harder.
RESILIENCE Resilience is related to elasticity and describes the ability of a string to return to its original length after being stretched. If a string is stretched too much or is subjected to wear and tear from abrasion and repeated stretching, it may not return to its original length an effect known as inelastic deformation. In a strung racket, where the strings are a constant length, the effect of inelastic deformation is a slight drop in tension every time a ball is hit. Strings with low dynamic stiffness are able to deform and recover more completely (so are more resilient), making them livelier and providing greater power. Over time, strings lose their resilience and return less energy to the ball, reducing power and making the strings feel dead.
TENSION STABILITY/MAINTENANCE/RETENTION The tension holding ability of the string. All strings are subjected to creep a gradual loss of tension over time that reduces playability but some strings are more creep resistant than others. A string with good tension maintenance is less susceptible to creep and maintains its characteristics longer, giving more consistent response over its usable life.
1. GOODWILL, S. R. and HAAKE, Steve (2004). Effect of string tension on the impact between a tennis ball and racket. In: HUBBARD, M., MEHTA, R. D. and PALLIS, J. M., (eds.) The Engineering of Sport 5. International Sports Engineering Association, 3-9.