Compression clothing is any garment engineered to apply consistent pressure to your body, typically your legs, arms, or abdomen. These garments squeeze your tissues with enough force to improve blood flow, reduce swelling, and support muscles during activity or recovery. They range from medical-grade stockings prescribed after surgery to the athletic sleeves and tights you see in gyms and on running trails. What they all share is a basic mechanism: external pressure pushes blood through your veins more efficiently and limits fluid buildup in your tissues.
How Compression Clothing Works
Your veins rely on one-way valves and muscle contractions to push blood back up toward your heart, fighting gravity the entire way. When those valves weaken or your muscles aren’t contracting (because you’re sitting, standing still, or recovering from surgery), blood can pool in your lower legs. This pooling causes swelling, heaviness, and in more serious cases, blood clots.
Compression garments counteract this by squeezing your legs from the outside, mimicking the effect of muscle contractions. The pressure narrows your veins slightly, which speeds up blood flow and helps the valves close more completely. Most medical-grade compression is “graduated,” meaning the pressure is strongest at the ankle and decreases as it moves up toward the knee or thigh. This gradient creates a pumping effect that actively pushes blood upward.
Compression Levels and What They Mean
Compression is measured in millimeters of mercury (mmHg), the same unit used for blood pressure. Garments fall into four standardized classes:
- Class I (18 to 21 mmHg): Light compression for mild swelling, tired legs, or early-stage varicose veins. Available over the counter.
- Class II (23 to 32 mmHg): Moderate compression for more pronounced varicose veins, post-surgical recovery, and moderate swelling.
- Class III (34 to 46 mmHg): Firm compression for chronic venous insufficiency, severe swelling, and lymphedema management.
- Class IV (49+ mmHg): Very firm compression reserved for the most severe cases of lymphedema and venous disease.
Athletic compression clothing typically falls below or within the Class I range. It provides enough pressure to reduce muscle vibration during exercise but not enough to require a prescription. If you’re buying compression for a medical condition, the class matters, and your provider will specify the right level.
Medical Uses
Compression therapy has a long track record in medicine, and it remains a frontline treatment for several circulatory conditions.
For chronic venous insufficiency, where weakened vein walls and faulty valves allow blood to flow backward and pool in the legs, graduated compression stockings help push blood back toward the heart. This reduces the swelling, skin changes, and leg ulcers that come with the condition. For deep vein thrombosis (DVT) prevention, hospitals use intermittent pneumatic compression devices: inflatable cuffs that rhythmically squeeze your legs while you’re immobile after surgery. These devices not only push blood through your veins but also trigger the release of natural clot-preventing substances in your body.
Lymphedema, the chronic swelling caused by a damaged or blocked lymphatic system, is another major application. Compression sleeves and stockings help move lymph fluid out of the affected limb and prevent it from accumulating. People with orthostatic hypotension (a sudden drop in blood pressure upon standing) or postural tachycardia syndrome (POTS) also benefit. One study in a pediatric POTS population found that combined leg and abdominal compression reduced heart rate response to standing by 24 beats per minute compared to no compression. Notably, garments that compressed the abdomen were more effective than leg-only compression at preventing blood pressure drops, because a large volume of blood pools in the abdominal area when you stand.
Athletic Performance and Recovery
Compression tights, calf sleeves, and arm sleeves are popular among runners, weightlifters, and team sport athletes. The main performance benefit is reduced muscle oscillation: when your foot strikes the ground during a run, your soft tissue vibrates, and compression limits that vibration. Less oscillation can mean less muscle fatigue and lower impact forces over long distances.
The evidence on raw power and strength is less convincing. A meta-analysis covering 45 comparisons from 18 studies found no significant effect of compression garments on power output or strength. So if you’re hoping compression shorts will help you squat more weight, the data doesn’t support that.
Where compression clothing shows more consistent benefits is in recovery. Wearing compression during the first 24 hours after intense exercise reduces delayed onset muscle soreness (DOMS) and perceived fatigue. The effect isn’t as strong as a professional massage, but it’s a passive intervention you can use while going about your day. After that initial 24-hour window, intermittent use still helps, though the benefit diminishes over time. Compression also appears to lower blood lactate concentration during endurance exercise, which may help sustain effort during prolonged activity.
Materials and Construction
Compression fabrics are built around elastane (the generic name for Spandex), usually blended with nylon or polyester. The elastane provides stretch and recoil, the property that creates pressure against your skin. Most garments contain 10 to 30 percent elastane by weight, with the base fiber handling durability and moisture management. Nylon blends tend to feel softer and smoother, while polyester blends dry faster and cost less.
Two main knitting methods create different types of compression. Circular knitting produces seamless tubes with four-way stretch, common in compression socks, tights, and athletic tops. These feel smooth and conform closely to your body. Warp knitting creates a tighter, more structured fabric often called power mesh or powernet, which shows up in medical braces and shapewear where stronger, more targeted support is needed.
Getting the Right Fit
Fit determines whether compression clothing actually works. A garment that’s too loose won’t generate enough pressure; one that’s too tight can restrict blood flow and cause discomfort. For medical compression stockings, sizing requires specific body measurements taken at precise anatomical points.
For knee-length stockings, you need two measurements: calf circumference at its widest point, and the length from the back of your heel to the bend of your knee. For thigh-length stockings, add your upper thigh circumference measured at the buttock fold, plus the full length from your heel to that fold. These measurements should be taken first thing in the morning before any swelling develops, since your legs are at their smallest after a night of elevation.
Athletic compression is less precise. Most brands use standard small-through-extra-large sizing based on height and weight, though calf sleeves and arm sleeves usually go by circumference. If you’re between sizes, sizing down generally gives you more effective compression, but you shouldn’t have to struggle to get the garment on or feel numbness or tingling while wearing it.
Who Should Avoid Compression
Compression is not safe for everyone. The most important contraindication is peripheral artery disease (PAD), where the arteries supplying your legs are already narrowed. Adding external pressure on top of compromised arterial flow can reduce blood supply to your feet and toes, potentially causing tissue damage. Clinical guidelines recommend against compression therapy for people with advanced PAD. If you have known circulation problems in your legs, cold feet, or pain in your calves when walking, compression garments should only be used under medical guidance.
Other situations where compression can cause problems include active skin infections on the legs, untreated congestive heart failure (where pushing more fluid back toward the heart can worsen the condition), and areas with fragile or broken skin. For most healthy people using athletic compression, the risk is minimal, but if you notice any numbness, tingling, increased pain, or skin color changes while wearing a garment, remove it.