Stiffness (RA): the number that matters for your arm

Of all a racquet's specifications, stiffness is the least visible — you cannot see it on the shelf or feel it holding a still frame — and it matters most for one specific question: can your arm handle this racquet for two sets, three times a week?

What the RA scale measures

When the ball arrives, the frame flexes. The RA scale measures resistance to that flex in a standardized bench test: the higher the number, the stiffer the frame. In our catalog, values run from RA 54 to RA 75 — a narrow-looking band, but the difference between its ends is enormous in the hand.

The physics of the trade is direct:

• Stiff frame (high RA): flexes little, so it returns more energy to the ball. "Free" power — and a harsher impact transmitted to hand, elbow and shoulder.
• Flexible frame (low RA): absorbs part of the impact by flexing. More comfort, and a response many players describe as more controllable — but the power has to come from your swing.

Stiffness and pain: what is known

Tennis elbow is multifactorial — technique, playing volume, string, tension and conditioning all weigh in alongside the frame. But for the racquet's share of the problem, the biomechanics literature consistently points at impact shock and vibration transmitted to the arm, and stiffer frames transmit more.

The combination most associated with trouble is exactly what dominates the entry-level shelf: a light, stiff, head-heavy frame. Light, because it twists more on off-center impact; stiff, because it transmits shock instead of absorbing it; head-heavy, because it increases the lever on the elbow. Each factor alone is manageable — all three together, in a player whose technique is still developing, is the classic recipe for pain.

The obvious still needs saying: persistent pain is a case for a medical professional, and no racquet substitutes for that. What the right choice does is stop adding to the problem.

Reading the number in practice

The ruler we use in the catalog — the same thresholds as our recommendation filter:

• RA 62 or below — arm-friendly territory. Where to look first with any history of pain.
• RA 63 to 67 — the modern middle; the catalog's median sits at RA 64catalog median.
• RA 68 or above — power first; advisable only if your arm has never complained and you want a crisp response.

Three examples from the catalog, from the most flexible to the modern flexible classics:

Stiffness does not act alone

Two frames with the same RA can treat your arm differently, because the rest of the setup participates too:

• String and tension: a stiff polyester at high tension hardens any racquet; a multifilament at lower tension softens it. If you play with pain, the string is the cheapest adjustment before changing frames.
• Weight: mass absorbs shock. A slightly heavier frame (within what you can swing comfortably) tends to be gentler than an ultralight at the same RA.
• Contact point: off-center impact transmits more twist — part of the comfort of larger heads comes from forgiving those hits.

The summary

If free power is the priority and your arm has never complained, high RA is a legitimate trade. If you have ever felt your elbow after playing, look at RA 62 and below before any other spec — and treat weight and string as part of the same package.

In the catalog, every racquet's stiffness is measured on the full collection's ruler, and the quiz asks directly about pain history — when you report it, the filter treats comfort as a constraint, not a preference.