⚠️ Strings are not a treatment
Changing strings changes your equipment; it does not heal a tendon. If the pain lasts, wakes you at night or does not ease with rest, see a doctor or a physiotherapist before changing anything else. This article describes equipment; it gives no medical advice — and no tension "that heals".
🩺 The short version
- The criterion is stiffness. Our 102 polys range from 164.6 to 286.9 lb/in (median 220). In the same frame, that gap is worth 13 to 14 RCS points.
- The softest: Toroline O-Toro Snap (164.6), Toroline O-Toro (165.7) and Toroline O-Toro Spin (173.2) give an index of 24 to 25 in our example; the stiffest, Luxilon 4G (286.9), Babolat RPM Team (280.6) and Babolat Revenge (276), give 36 to 38.
- "Comfortable" is not "soft". Yonex Poly Tour Pro has the 2nd best comfort rating of the 18 polys assessed by testers, but it is only the 7th softest (220 lb/in).
- Tension does not make up for the string: 4 kg (about 9 lb) less removes 2 points; changing string can remove 14.
The usual advice for a sore elbow is to leave polyester. Many players do not: they value the control and spin a monofilament gives them. This article is for them. It does not say which poly is best — our 2026 ranking does that — but which one loads your setup the least.
🔎 1. Why sort by stiffness, not by score
A string's stiffness, in lb/in, says how much it resists being stretched: the higher it is, the harder the string. It is the only string property used by the site's RCS index, which combines frame stiffness (RA), string stiffness and tension into one firmness index of the setup, from "very comfortable" (below 20) to "very firm" (35 and above, the risk zone for the elbow).
A comfort rating, on the other hand, is an assessment: a tester describes a feeling at impact, which also depends on the gauge, tension and frame they used. It is useful, but it does not measure the same thing. For a sensitive arm, we therefore sort by stiffness first, and give the RCS index it produces.
In the tables below, the index is computed for one shared example: string at 22 kg (48.5 lb), in three racquets with an RA of 60, 65 and 70. It is not a recommended tension; it is a fixed point to compare strings with each other.
A note on method. A product page often groups several gauges under a single stiffness. When that stiffness is aligned on a measurement by the Tennis Warehouse University (TWU) lab, we show the one for the stiffest gauge TWU measured among the page's gauges. That can overstate the stiffness of another gauge on the product page, one measured softer (not always the finest), so the RCS index may look severe for that gauge. This is deliberate, out of caution for the arm. For your exact setup, the configurator's index is the one to trust.
🟢 2. The 15 softest polys in the catalogue
Every polyester in our catalogue at 200 lb/in or less, from softest to least soft. Out of 102, there are 15.
| # | String | Stiffness (lb/in) | RCS RA 60 | RCS RA 65 | RCS RA 70 |
|---|---|---|---|---|---|
| 1 | Toroline O-Toro Snap † | 164.6 | 23 | 24 | 26 |
| 2 | Toroline O-Toro † | 165.7 | 23 | 24 | 26 |
| 3 | Toroline O-Toro Spin † | 173.2 | 23 | 25 | 27 |
| 4 | Solinco Hyper-G Heaven | 175 | 24 | 25 | 27 |
| 5 | Isospeed Cream † | 177.7 | 24 | 26 | 27 |
| 6 | Toroline Absolute † | 180.6 | 24 | 26 | 28 |
| 7 | Toroline Cash † | 182.9 | 25 | 26 | 28 |
| 8 | Toroline Super Toro † | 189.7 | 25 | 27 | 29 |
| 9 | Luxilon Eco Rough | 190 | 25 | 27 | 29 |
| 10 | Toroline Snapper † | 190.9 | 25 | 27 | 29 |
| 11 | Yonex Poly Tour Air | 195 | 26 | 28 | 29 |
| 12 | Luxilon Element Rough † | 198.3 | 26 | 28 | 30 |
| 13 | Solinco Hyper-G Soft | 200 | 26 | 28 | 30 |
| 13 | Solinco Tour Bite Soft | 200 | 26 | 28 | 30 |
| 13 | Yonex Poly Air Rush | 200 | 26 | 28 | 30 |
† Stiffness aligned on a measurement by the Tennis Warehouse University (TWU) lab: when the product page groups several gauges, it is the one for the stiffest gauge TWU measured. The other values come from our product pages: they are not aligned on a lab measurement and may differ from one, in either direction. RCS index: string at 22 kg, comparison example.
Two readings. First, even the softest polyester stays above 20, the "very comfortable" threshold, in all three examples: a soft poly is a less firm poly, not a comfortable string in the index's sense. Second, the frame shifts the whole table: the same O-Toro goes from 23 in an RA 60 frame to 26 in an RA 70 frame. The configurator runs that calculation for your exact racquet.
🔴 3. The 21 firmest
At the other end, 21 polys in the catalogue are at 240 lb/in or more. In an RA 65 racquet at 22 kg, they give an index of 32 to 38; in an RA 70 frame, 34 to 39, and most of them then reach the "very firm" threshold (35 and above).
- 240 lb/in (index 32 at RA 65): Babolat RPM Blast, Luxilon Original;
- 242.9 to 248 lb/in (33): Tecnifibre Black Code 4S †, Tecnifibre Razor Code †, Head Master, Luxilon Timo 117, Solinco Confidential, Yonex Poly Tour Tough, Luxilon Ace 118;
- 249.7 to 255 lb/in (34): Tecnifibre Black Code †, Solinco Barb Wire, Weiss Cannon Ultra Cable, Babolat RPM Hurricane, Luxilon Ace 112, Solinco Tour Bite;
- 260 to 262 lb/in (35): Babolat Pro Hurricane, Solinco Tour Bite Diamond Rough, Luxilon 4G Rough;
- 276 lb/in (36): Babolat Revenge †;
- 280.6 lb/in (37): Babolat RPM Team †;
- 286.9 lb/in (38): Luxilon 4G †.
† Same meaning as under the first table: stiffness aligned on a TWU measurement, the stiffest gauge measured when the product page groups several.
These are not bad strings: several rank very well with testers, for their control and durability. But if your elbow complains, this is the list where changing string pays off most.
⚖️ 4. Felt comfort versus stiffness: the gap
18 of our polys are covered by a synthesis of specialist tester reviews, and their product page carries a comfort score out of 10 that takes it into account. If feel and stiffness said the same thing, the comfort order and the softness order would match. They often follow each other, but not always:
| String | Stiffness (lb/in) | Softness rank (of 18) | Product page comfort score | Comfort rank (of 18) |
|---|---|---|---|---|
| Yonex Poly Tour Pro | 220 | 7th | 8.6 | 2nd |
| Solinco Mach-10 † | 222.3 | 8th | 8.8 | 1st |
| Solinco Confidential | 245 | 14th | 7.3 | 10th (tied) |
| Solinco Hyper-G † | 218.3 | 6th | 7.6 | 9th |
| Toroline O-Toro † | 165.7 | 1st | 8.1 | 3rd |
| Yonex Poly Tour Rev | 205 | 2nd | 8.0 | 4th |
† Same meaning as under the first table. Ranks computed on the 18 polys covered by tester reviews. Where stiffness is tied (Head Hawk Touch and Völkl Cyclone, 215 lb/in), the order is alphabetical.
Two cases stand out. Yonex Poly Tour Pro: 2nd for comfort, but 7th for softness. Testers describe it as round and soft at impact; its stiffness is exactly the catalogue median (220 lb/in). Solinco Mach-10: 1st for comfort, but 8th for softness (222.3 lb/in). Conversely, Solinco Hyper-G is 6th for softness but only 9th for comfort. The synthesis says so itself: comfort there is often inferred from how a string is described — soft or firm, round or shaped — rather than observed directly.
Both pieces of information are true at once: one describes what the player feels, the other what the string does. For a sensitive arm, we look at stiffness first, because it is what the RCS index uses and because it describes the string, not a feeling. The two polys that rank in the top four on both criteria are Toroline O-Toro (1st for softness, 3rd for comfort) and Yonex Poly Tour Rev (2nd for softness, 4th for comfort).
🔧 5. String, frame, tension: the order of the levers
The RCS formula lets us compare the three levers on a worked example. In an RA 65 racquet, with Luxilon 4G at 22 kg (index 38):
- Change the string to Toroline O-Toro, same racquet, same tension: 38 → 24, 14 points.
- Change the frame to an RA 60, same string, same tension: 38 → 36. Conversely, an RA 70 frame takes the 4G up to 39.
- Lower the tension by 4 kg (about 9 lb), same racquet, same string: 38 → 36.
In this formula, 1 kg of tension is worth half an index point, one RA point a third of a point, and 10 lb/in of string stiffness a little over one point. The string is the main lever, by far. We give no tension "for the elbow": no measured source sets one, and tension moves the index only a little.
🧵 6. What about hybrids?
Stringing a polyester in part of the racquet and a multifilament in the other is an option often mentioned for keeping some poly. We do not put numbers on it here: only 11 of our 45 multifilaments have a stiffness aligned on a lab measurement, and a pre-packed set has no measurement of its own in our database; an index computed on them would show a precision it does not have. For string families softer than polyester, see our guide to the best tennis strings for tennis elbow and our polyester vs multifilament comparison.
⚠️ History of tennis elbow
Keeping a polyester is a playing choice, not a health choice. Even the softest in this table is still a monofilament: generally firmer than a multifilament, and clearly firmer than natural gut. If your elbow has already been affected, leaving polyester generally remains the more prudent choice; this article only serves to limit the damage if you do not.
❓ FAQ — polyester strings and tennis elbow
Which polyester string should I use with tennis elbow?
If you keep a polyester, pick one of the softest. In general, a multifilament or natural gut remains a more prudent choice than a polyester. In our catalogue of 102 polys, the three least stiff are Toroline O-Toro Snap (164.6 lb/in), Toroline O-Toro (165.7) and Toroline O-Toro Spin (173.2). In a racquet with an RA of 65 strung at 22 kg, they give an RCS index of 24 to 25, against 38 for the stiffest.
Is a polyester rated as comfortable necessarily soft?
No. Yonex Poly Tour Pro has the 2nd best comfort rating of the 18 polys covered by tester reviews, but it is only the 7th softest (220 lb/in). Feel at impact and stiffness do not say the same thing; the RCS index only uses stiffness.
Is lowering the tension enough to protect the elbow with a polyester?
Not according to the site's RCS index: 4 kg (about 9 lb) less removes 2 points, while replacing Luxilon 4G (286.9 lb/in) with Toroline O-Toro (165.7 lb/in) removes 14 in the same frame. The string choice matters far more than the tension. Strings are not a treatment: persistent pain is a matter for a doctor.