The mechanics of string-related arm pain
When a ball strikes your strings, kinetic energy transfers through the string bed, frame, shaft, grip, and into your arm. How much energy your arm absorbs depends entirely on how stiff this chain is at every link.
Stiff strings absorb less of that energy — they transfer more shock directly to your hand and arm. Elastic strings absorb more energy — they cushion the impact before it reaches your body. This is the core tradeoff between polyester and natural gut, and it matters enormously for arm health.
| String type | Typical stiffness | Arm impact |
|---|---|---|
| Polyester | 200–270 N/mm | Highest shock transmission |
| Multifilament | 130–180 N/mm | Moderate — meaningfully softer than poly |
| Synthetic gut | 120–160 N/mm | Moderate to soft |
| Natural gut | 85–145 N/mm | Lowest shock — most arm-friendly available |
The worst strings for a bad arm
Full polyester is the hardest string on your arm. This isn't a matter of opinion — it's well-established and acknowledged throughout the sport. The problem is compounded by three factors that tend to stack:
- Poly is inherently stiff. Even a fresh set transmits more impact shock than any other string type.
- Poly loses tension fast. A set that was strung at 55 lbs is playing at 47–50 lbs within a few weeks. Dead tension means the string is both stiff and lifeless — you lose the power it was supposed to provide while the stiffness remains. This is the worst combination.
- Players over-tension poly. A common mistake is stringing poly at the same tension as a multifilament and wondering why it feels harsh. Poly should be strung 10–15% lower to account for its higher stiffness.
If you're currently playing with old polyester — say, strings you haven't changed in more than 6–8 weeks — that dead string is likely contributing more to your arm pain than a fresh setup would. Dead poly is effectively stiffer than fresh poly because it has no elasticity left to absorb impact. Change the strings first before drawing conclusions about your setup.
The best strings for arm comfort, in order
1. Natural gut (mains or full)
Natural gut is the gold standard for arm comfort. Its elasticity — the highest of any string material — absorbs impact energy before it reaches your arm. If you're dealing with serious arm problems and haven't tried gut, this is the single biggest string-related change you can make. The improvement is usually immediate and significant.
2. Multifilament
Made from hundreds of microfibers bonded together, multifilament strings mimic some of gut's elasticity at a fraction of the cost. They're a strong first step for arm-conscious players who aren't ready to commit to gut pricing. Well-regarded multifilaments we stock at Tennis Lab FX include Wilson NXT, Tecnifibre X-One Biphase, and Babolat Xcel.
3. Gut mains in a hybrid
Natural gut mains with polyester crosses. The mains contact the ball first and do most of the energy-absorbing work — so gut in the mains delivers most of gut's arm benefit at roughly 60% of the cost of a full gut job. This is the most practical high-performance option for arm-conscious players who still want spin from poly crosses.
4. Synthetic gut
A single nylon core with wraps — more elastic than polyester, cheaper than gut or multifilament. A reasonable starting point if cost is the primary concern. Not as arm-friendly as multifil or gut, but significantly better than stiff poly.
Tension matters as much as string type
Lower tension = more elasticity = less shock. Every 5 lbs you drop your tension increases the string bed's ability to cushion impact. For an arm-conscious player, string in the lower third of your frame's recommended range.
If your frame recommends 50–62 lbs, try 52–54 lbs. Do not string polyester at high tension expecting control benefits if your arm is already complaining — the additional stiffness will only make things worse. Comfort and tension work in the same direction: lower serves both.
The frame matters too
All the string advice in the world is limited if your frame is contributing to the problem. Frame stiffness (measured as RA) determines how much vibration the shaft transmits regardless of string choice.
- RA above 68: Very stiff — amplifies shock significantly. String-related improvements will be partially offset.
- RA 62–68: Moderate. String choice makes a meaningful difference.
- RA below 62: Flexible — the frame itself absorbs much of the impact. String is still important but the frame does more of the work.
If you're playing a stiff, light frame strung with poly at high tension, you've assembled the most arm-unfriendly setup available. Frame stiffness and string stiffness stack — the combined effect is more than either one alone.
Our recommendation at Tennis Lab FX
Start with multifilament at the lower end of your frame's tension range and play two weeks. If that doesn't meaningfully reduce discomfort, move to gut mains in a hybrid. Full gut is the option of last resort for arm issues — it works, but the cost is higher and the improvement beyond gut mains is usually modest.
Come in and we can look at your current setup, measure the frame's stiffness, and tell you exactly where the problem is most likely originating. In most cases, a string change is the fastest and cheapest path to improvement.
String type: natural gut or multifilament (avoid full poly). Tension: lower third of your frame's range. Frame RA: below 66 if possible. Gauge: 17g or thinner adds marginal elasticity. Restring: fresh strings always — dead poly is worse than dead gut.
Come in and we'll check your current setup.
We can measure your frame's RA, assess your string condition, and give you a specific recommendation — in one visit.