Pick up a pack of premium multifilament and somewhere on the back you will find a comfort claim with a number attached — Tecnifibre has marketed its multifilaments around "comfort and power," and various brands quote figures like "up to 20% more comfort" or shock-absorption percentages versus a house reference string. That single percentage is the engine of this tennis string review, because it is doing a lot of quiet work: it is the number most likely to sell a frustrated, elbow-sore intermediate on the idea that string construction can resolve the comfort-versus-power standoff. Our verdict, stated plainly up front: the number points at something real — multifilament and natural gut constructions are genuinely lower in dynamic stiffness than co-poly — but the percentage as printed measures far less than the buyer thinks it does.
What the number is actually measuring
When a string is described as "softer" or "more comfortable," the underlying physical quantity is almost always stiffness, usually expressed as dynamic stiffness in newtons per millimetre (N/mm) or, in older databases, kilograms per centimetre. It describes how much the string bed deflects under a given impact load. A lower number means the bed gives more, returns less shock to the frame and hand, and lengthens dwell time fractionally.
The independent reference most testers and engineers lean on here is the work that Tennis Warehouse University (TWU) compiled under Crawford Lindsey, whose string database lists stiffness values measured on a consistent rig rather than on a player's arm. In that data set the spread is wide and consistent: co-polyester strings cluster high (roughly 200–240+ N/mm in many entries), nylon and multifilaments sit notably lower, and natural gut is among the lowest stiffness strings measured.
So when a manufacturer says "20% more comfort," the honest translation is usually "this string tested roughly 20% lower in stiffness than the reference string we compared it against." That is a defensible mechanical statement. The trouble starts when "lower stiffness" is read as "will not hurt your arm," which is a different and much larger claim.
How we evaluated
We did not string a racquet or swing one for this piece, and we will not pretend otherwise. This is a synthesis. We weighed three kinds of evidence:
- Published manufacturer specs and claims — gauge, material, marketing comfort figures — read skeptically and treated as the seller's own number.
- Independent measured data, primarily the TWU/Lindsey string database stiffness and tension-loss figures, which carry the most weight here because the rig is consistent across strings.
- Aggregated tester and owner feedback from string reviews and retailer review sections, used to corroborate or challenge the lab numbers — useful for patterns, weak on any single data point.
Where the manufacturer claim and the independent stiffness data agree, we say the evidence is strong. Where comfort rests only on the brand's own number, we flag it.
What construction actually drives the feel
Stiffness tracks construction more reliably than it tracks price or marketing. The four broad families line up like this:
| Construction | Typical dynamic stiffness | What the number suggests | Main tradeoff |
|---|---|---|---|
| Co-polyester (poly) | High (~200–240+ N/mm in TWU data) | Stiff, low-powered, spin-friendly | Hardest on the arm; drops tension fast |
| Solid-core synthetic gut | Moderate–high | Middle of the road, predictable | Jack of all trades, master of none |
| Multifilament | Low–moderate | Soft, comfortable, powerful | Durability; frays before it breaks |
| Natural gut | Among the lowest measured | Softest, best tension maintenance | Price; weather sensitivity |
The numbers in that table are stiffness ranges drawn from the TWU database and should be read as orientation, not as a spec sheet for any one string — individual strings cross these lines. But the ordering is consistent across the independent data, and it is the ordering, not the exact figure, that the comfort claim is really riding on.
The false choice — and where the tradeoff actually lives
The frustration this piece is written for is the belief that you must choose comfort or power. Stiffness data undercuts that belief in a useful way: low stiffness and high power are not opposed. A softer string bed deflects more and returns more energy, which is why multifilament and natural gut are simultaneously among the most comfortable and most powerful constructions in the measured data. The poly that punishes your elbow is also, in TWU's stiffness figures, among the least powerful at a given tension — players accept that low power and recover spin and control elsewhere.
The real tradeoff a low-stiffness string asks you to accept is not power. It is durability and, to a lesser degree, precise control. Multifilaments are bundles of fibres; as those fibres break the string frays and notches and the feel degrades before the string snaps. That is the genuine cost the comfort number does not print. The honest workarounds are the familiar ones — a hybrid setup pairing a softer cross with a firmer main, or a thinner gauge for bite at the expense of life — and they are tradeoffs, not fixes.
What the number does not measure
This is where a comfort percentage earns its skepticism. A stiffness figure measured on a rig says nothing about:
- Tension loss over time. Co-poly sheds tension fast and stiffens as it ages; a string that tested comfortable on day one can feel boardy in two weeks. TWU's tension-loss data matters as much as the stiffness headline.
- Your arm. No published string figure was measured against your specific elbow, your grip, your swing speed, or an existing injury. Comfort is partly a property of the string and partly a property of the player, and the percentage only describes the first half.
- Off-center feel and string movement, both of which owners report heavily and labs capture poorly.
A 20% lower stiffness number is a real, attributable mechanical fact. It is not a clinical claim about tennis elbow, and no reputable string database presents it as one.
Who this is for, and who it isn't
This is for the intermediate or club player with arm-comfort concerns who has been stringing co-poly at full tension and wondering why their elbow complains. The construction data says a multifilament or natural-gut bed is the lowest-stiffness move available, and the comfort claim is, for once, pointing the right direction.
This isn't for the heavy-topspin string-breaker who needs a frame of poly to survive a week — for them the answer is a hybrid, not a full multifilament — or for anyone expecting a string to substitute for technique, fit, or a coach's read on the injury.
The screenshot line: lower dynamic stiffness is the most reliable, independently measured comfort signal in a string spec — and multifilament and natural gut, not soft poly, are where that number actually lives.
What this didn't answer
We can tell you which constructions test softer and why the comfort-versus-power framing is a false one. We cannot tell you, from published data, how much a 20% stiffness reduction lowers your injury risk — the controlled studies linking specific string stiffness to elbow load in recreational players are thin, and we will not invent them. For the next step, look at the TWU stiffness and tension-loss tables for the specific strings on your shortlist, and treat any in-vivo comfort claim as a hypothesis to confirm against owner reviews and your own arm, not a settled result.
Evidence grade for the central claim — that lower dynamic stiffness, found in multifilament and natural gut, is the reliable comfort signal: Moderate-to-strong on the mechanics, Weak on the leap from stiffness to injury prevention.