There are four official compression classes. There’s only one that does what athletes think compression socks do. And it’s not the one most “performance” brands actually sell.
The four classes, in plain numbers
Compression on a sock is measured in mmHg — millimeters of mercury — the same pressure unit used for blood pressure. It refers to the pressure applied at the ankle, where compression is always highest. As the sock goes up the leg, the pressure decreases — that’s the “graduated” part. It’s what pushes deoxygenated blood back up toward the heart instead of pooling in the calves.
The international standard:
| Class | Pressure (mmHg) | Typical use |
|---|---|---|
| Class 1 | 18–21 | Light support — mild varicose veins, long-haul flights, all-day standing |
| Class 2 | 23–32 | Medical recovery — post-surgery, chronic venous insufficiency, high-intensity athletic recovery |
| Class 3 | 34–46 | Serious lymphedema management — typically prescribed and supervised |
| Class 4 | 49+ | Severe medical use — only on prescription, often hospital-administered |
Most of what’s marketed as “athletic” or “fitness” compression sits at 8–15 mmHg — which is technically below even Class 1. It’s a regular sock with a slightly tighter weave at the ankle.
That category of product exists because it sells. It’s cheap to manufacture, looks the part, and most consumers can’t measure the difference. But it produces almost none of the physiological effects that make compression socks actually useful.
What Class 2 actually does in the body
The mechanism is mechanical, not magical. Graduated 23–32 mmHg pressure does three measurable things:
- Improves venous return. Calf-muscle contraction is the body’s main mechanism for pushing venous blood back to the heart. Class 2 compression amplifies that pump significantly — roughly equivalent to active recovery during passive sitting.
- Reduces interstitial fluid buildup. The pressure gradient prevents fluid from accumulating in the lower leg during prolonged standing or post-exercise inflammation. This is what reduces the “puffy calves” feeling after long efforts.
- Stabilizes muscle vibration. During running and high-impact loading, calf muscles oscillate. Compression dampens that oscillation, which has been shown in some studies to reduce muscle damage markers (CK, myoglobin) post-exercise.
These mechanisms are why physiotherapists routinely prescribe Class 2 socks for patients recovering from leg surgery, athletes returning from injury, and elderly patients with chronic venous insufficiency. The same mechanism is what serious endurance athletes have been using for the past 15 years.
The performance literature is more nuanced. The strongest evidence is for post-exercise recovery — reduced soreness, faster perceived freshness, lower delayed-onset muscle soreness (DOMS) the day after. In-event performance gains are smaller and depend heavily on the discipline. For sub-maximal efforts of 20+ minutes (marathon, Hyrox, triathlon), there’s a small but consistent benefit. For pure max-strength work, the benefit is mostly in recovery.
Why athletes prefer Class 2 specifically
Most serious endurance athletes have tried both Class 1 (“performance” or “fitness” compression) and Class 2 (medical-grade). The almost-universal feedback:
- Class 1 feels like a slightly snug sock. It’s comfortable. It also doesn’t seem to do anything in particular, which is correct — at 8–15 mmHg there’s minimal physiological effect.
- Class 2 feels noticeably tight when you put it on, then disappears within a few minutes. Recovery the next day is noticeably better. Calves feel less heavy after long sessions. This effect is reproducible and large enough that athletes can feel it within 1–2 wear cycles.
There’s a third category — Class 3 (34+ mmHg) — that some elite athletes experiment with. Most stop. At Class 3 the sock is hard to put on, often uncomfortable to keep on for hours, and provides only marginal additional benefit over Class 2 for the average athlete. Class 3 is designed for actual medical lymphedema management; it’s not a “more is better” upgrade for sports.
For 95% of athletic use cases, Class 2 (23–32 mmHg) is the right answer.
Why most “performance” socks aren’t Class 2
If Class 2 is the right answer, why isn’t every fitness brand selling it?
A few reasons:
- Production cost. Class 2 requires precision circular knitting on medical-grade machines. The yarn has to be specified to retain compression after dozens of washes. This is meaningfully more expensive than producing a Class 1 fashion sock.
- Returns and complaints. Class 2 feels different. First-time buyers sometimes complain that it’s “too tight” because they’re expecting the soft Class-1 fitness compression. Volume retailers don’t want the support burden.
- Marketing ambiguity. “Compression sock” is an unregulated term in athletic apparel in most jurisdictions. A brand can sell a 10 mmHg sock as a “compression sock” with no false claim. There’s no incentive to specify mmHg unless the product is actually Class 2.
The result is that the consumer-grade “performance compression” category is dominated by Class 1, while real Class 2 is concentrated in three places:
- Specialist medical-compression brands (Bauerfeind, Sigvaris) — clinical look, high price
- A handful of premium endurance brands (CEP Run, Compressport, STOX) — at the €30–45 price point
- Custom B2B suppliers (us, a small number of others) — sold by the box to gyms and race organizers
Why this matters if you’re a gym owner
If you’re selling branded compression at your gym, the spec matters more than most owners realize.
A Class 1 sock with your logo will sell once. Members will try it, find it underwhelming compared to their CEP, and not re-buy. Worse — they’ll associate your brand with “okay merch sock,” which is hard to recover from later.
A Class 2 sock with your logo will sell, get worn, get re-bought, and most importantly, replace the CEP and STOX in members’ rotation. That’s how a merch line becomes a category instead of a one-off T-shirt drop.
The cost difference at the wholesale level is small — a few euros per pair. The downstream difference in member behavior is enormous.
How to verify what you’re buying
If you’re evaluating a custom-sock supplier, three quick checks:
- Ask for the mmHg spec, on paper. “Compression” without a number is a red flag. The spec sheet should say 23–32 mmHg or equivalent.
- Ask what testing they use. Reputable Class 2 manufacturers test on equipment like Swisslastic AG — the same equipment medical-compression brands use to verify their batches.
- Ask for a sample. A 30-second wear test tells you everything. Class 2 feels distinct from Class 1 within seconds; if you can’t feel a noticeable squeeze, it’s not Class 2.
How this slots into our product
The Compression Goods knee-high sock is built to Class 2 spec — 23–32 mmHg graduated, 53% Polyamide / 32% Polypropylene microfiber / 15% Elastane, knit on Swisslastic-tested equipment at our specialized compression knit partner.
It’s the same compression class an elite Hyrox athlete or sub-3 marathon runner is already wearing — just with your gym’s brand on it. That’s the entire reason it works as merch, and the entire reason a Class 1 alternative wouldn’t.
Read more on the product page, or start a design to see what your brand looks like on it.
