Compression clothing: what it actually does

Compression gear is marketed as a fix for everything from stronger legs to twice-faster recovery. The real picture is narrower and duller: a few situations where it measurably helps, and many where it is just a snug shirt. Here is what is known, with numbers.

What compression actually does

The fabric is usually nylon or polyester with 15–25% elastane. Pressure on soft tissue has three effects you can measure:

• It reduces muscle oscillation. When you run, your calf and quad wobble after every ground contact. Compression damps that vibration, which is linked to slightly less muscle micro-damage over long distances.
• It supports venous return. Graduated pressure — higher at the ankle, lower toward the knee — mechanically helps blood and lymph move upward.
• It sharpens joint position sense. Pressure on the skin gives your brain extra information about where the knee or elbow is in space.

What it does not do: it does not burn the fat underneath it, it does not permanently reshape your waist, and it does not replace an 8–10 minute warm-up.

How much pressure to look for

Pressure is measured in millimetres of mercury (mmHg), and it is the only number on the label that means anything:

• 8–15 mmHg — light, for all-day wear and long travel.
• 15–20 mmHg — the sports standard, and the range used in most recovery research.
• 20–30 mmHg — medical class 1; useful for swelling and venous problems, but check with a doctor first.
• 30–40 mmHg and above — prescription territory only.

A large share of compression tights and tops in sports shops list no pressure at all and realistically deliver 5–10 mmHg. That is tight clothing, not compression. If there is no mmHg figure on the label, treat it as ordinary kit and expect nothing special.

Does it improve performance?

Short answer: barely. Reviews of running studies find differences in running economy and 5 km or 10 km times on the order of 0–1%, which sits inside normal day-to-day variation from sleep and hydration. For jump height, maximal strength and rep counts there is essentially nothing — a 5x5 squat at 85% will not move because of your tights.

If compression helps you feel settled before a race, or stops your thighs chafing over 20 km, that is a perfectly good reason to wear it. Just do not budget seconds for it.

Recovery: where it earns its place

The most consistent findings are about recovery after eccentric-heavy work: downhill running, a long race, the first hard leg session after a few weeks off. Wearing compression for 12–24 hours afterwards typically reduces muscle soreness and swelling — self-rated soreness on a 0 to 10 scale comes out roughly 1 point lower at 24 and 48 hours. That is small, but noticeable if you train 5 times a week.

In practice:

1. After a race longer than 15 km, or a session like 5x5 squats plus 3x12 lunges, put compression tights on within 30 minutes.
2. Wear them 12–24 hours, including overnight if that is comfortable; for sleeping, 15–20 mmHg is the ceiling.
3. The next day, take them off for 2–3 hours and check your skin — no deep marks, no pins and needles.

Getting the size right

Size is chosen by circumference, not by height and weight. Measure in the morning, before any daily swelling appears:

• ankle — the narrowest point, about 2 cm above the ankle bone;
• calf — the widest point;
• thigh — 10 cm above the top of the knee.

If you fall between two sizes, graduated socks are sized off the ankle measurement, and when in doubt the lower-pressure option is the safer one. The test after 30 minutes of wear: no tingling, warm toes, and skin marks that fade within a few minutes.

Care and lifespan

Elastane loses its stretch to fabric softener, heat and tumble dryers. Wash at 30 °C, skip the softener, dry in the shade and keep the garment off radiators. With 3–4 uses a week, expect 6–9 months, or 50–70 washes, before the pressure drops noticeably. Two garments in rotation last longer than one worn constantly.

When to see a doctor

Compression is not harmless in every condition. Talk to a doctor before wearing it regularly, or immediately, if you have:

• swelling in one leg only, with calf pain, redness and warmth — especially after surgery, a cast, or a flight over 4 hours (possible deep vein thrombosis);
• known peripheral arterial disease, where compression can further reduce blood flow;
• diabetes with neuropathy, or any loss of sensation in the foot;
• open wounds, eczema or a skin infection under the fabric;
• tingling, pale or cold toes, or pain that increases while wearing the garment — take it off straight away;
• swelling in both legs that appears without training (that needs a cause, not a cover-up).

The short version

• No stated mmHg means tight clothing, not compression; the sports range is 15–20 mmHg.
• The performance effect is 0–1% — do not plan around it.
• The real benefit is recovery: 12–24 hours of wear after a long race or eccentric-heavy session.
• Size by ankle, calf and thigh circumference, measured in the morning.
• Tingling, cold toes, one swollen leg or calf pain — take it off and see a doctor.