Underwear for Running: What to Look For

Quick answer

For running, prioritize a snug, supportive brief made from moisture-wicking fabric like Supplex® or Modal. Look for flat seams, a contour pouch for support, and a waistband that stays put without digging. If you chafe easily, choose a seamless back and avoid cotton. The Cocksox CX76N Supplex Sports Brief and CX76MD Modal Sports Brief are two strong options that meet these criteria.

Running demands underwear that moves with you, not against you. The wrong pair can cause chafing, bunching, and distraction that ruins your stride. The right pair disappears under your shorts, manages sweat, and keeps everything supported.

This guide gives you concrete decision rules to choose running underwear that works for your body and your training. We'll cover fabric, fit, support, and seam construction so you can stop guessing and start running comfortably.

Fabric: The First Decision Rule

If you run longer than 30 minutes or sweat heavily, choose a synthetic performance fabric. Supplex® is a nylon that wicks moisture, holds its shape, and feels soft. Modal is a natural, sustainable fabric that is silky and breathable, but it absorbs more moisture than Supplex®. Mesh fabrics are ultra-breathable and great for hot conditions, but they offer less structure. Cotton is a poor choice because it holds sweat, stays wet, and causes chafing.

For most runners, Supplex® or a Supplex®-blend brief is the safest bet. It dries quickly, resists odor, and keeps its fit run after run. If you prefer a softer, more luxurious feel for shorter runs or everyday wear, Modal works well. Mesh is best for intense heat or when you want maximum airflow.

• Avoid cotton for any run longer than a warm-up.
• Look for fabric that explicitly says moisture-wicking or quick-drying.
• Mesh is breathable but may not provide enough support for high-impact running.

Fit: Snug, Not Tight

Running underwear should fit like a second skin—close enough to prevent movement, but not so tight that it restricts circulation or digs into your waist. A brief cut stays in place better than a loose boxer because there's less fabric to bunch. If you prefer more coverage, a boxer brief with a snug fit can work, but check that the legs don't ride up.

The waistband should sit flat against your skin without rolling or leaving marks. If you can pinch more than an inch of fabric at the hip, it's too loose. If you see red marks after a run, it's too tight. Adjust your size accordingly; most brands offer a size chart based on waist measurement.

• Measure your waist and compare to the brand's size chart before buying.
• If you're between sizes, size down for running to avoid shifting.
• Test new underwear on a short run before a long one.

Support and Chafe Prevention

A supportive pouch keeps your anatomy in place, reducing bounce and friction. Cocksox® briefs feature a contour pouch designed for enhanced support. Seams are the enemy of chafe-free running: flatlock seams or seamless construction reduce rubbing. Look for a seamless wrap-around back, like on the CX76 series, to eliminate seams where you sit and stride.

Piping and edges should be smooth, not raised. If you're prone to chafing between the thighs, a brief with a snug leg opening is better than a loose boxer. Some runners use anti-chafe balm, but the right underwear can often solve the problem entirely.

• Choose flat seams or no seams in high-friction areas.
• A contour pouch improves support and reduces movement.
• If you chafe between thighs, consider a brief over a boxer.

Waistband and Leg Openings

The waistband is a common failure point. A narrow, streamlined waistband like the one on the CX76MD Modal Sports Brief sits discreetly under shorts and won't roll. Elastic should be covered or soft against the skin. Leg openings on briefs should have gentle elastic that stays put without cutting in. On boxer briefs, check that the leg hem doesn't ride up; if it does, the fit is wrong or the fabric lacks stretch.

For swim training or cross-training, the CX04 Drawstring Swim Brief has an internal drawstring for extra security, but it's designed for pool use, not running. Stick to dedicated running underwear for best results.

• Waistband should lie flat and not roll during movement.
• Leg openings should stay in place without pressure.
• Avoid drawstrings for running; they can create bulk under shorts.

Decision rules for buying running underwear

• If you run longer than 30 minutes or sweat heavily: Choose Supplex® or another synthetic moisture-wicking fabric. Avoid cotton and Modal for long runs because they absorb moisture. Supplex® briefs like the CX76N keep you dry and chafe-free.
• If you have sensitive skin or prefer a softer feel: Modal is a natural, sustainable fabric that is silky and breathable. It works well for short runs or everyday wear. The CX76MD Modal Sports Brief offers comfort without sacrificing support.
• If you run in hot, humid conditions: Mesh fabric provides maximum breathability and freshness. Look for a mesh brief with a supportive pouch. The CX76ME Mesh Sports Brief keeps you cool when things heat up.
• If you chafe easily between the thighs: Choose a brief cut over a boxer to minimize fabric movement and friction. Ensure seams are flat or seamless. A seamless back like on the CX76 series reduces chafing.

Product facts that matter for runners

• CX76N Supplex Sports Brief: Made from high performance Supplex® fabric, features the Cocksox contour pouch for maximum comfort support, a butt hugging seamless wrap around back and robust piping. Supplex® wicks moisture and holds shape, the contour pouch supports, and the seamless back reduces chafing—ideal for running.
• CX76MD Modal Sports Brief: Made from luxuriously silky Modal fabric, features the Contour Pouch for maximum comfort, a butt hugging seamless wrap around back and a specially designed narrow waistband for a streamlined discreet profile. Modal is soft and breathable for shorter runs or sensitive skin, and the narrow waistband stays discreet under shorts.
• CX76ME Mesh Sports Brief: Features ultra-soft breathable mesh fabric that feels soft against the body and gives ultimate freshness, with the unique Cocksox contour pouch and a butt hugging seamless wrap around back. Mesh maximizes airflow for hot weather runs, while the contour pouch and seamless back maintain support and reduce friction.

Who this guide is for

Best for

• Runners who want to prevent chafing and stay dry
• Active men seeking supportive underwear for high-impact activities
• Anyone looking for moisture-wicking briefs for running

Not for

• Those who prefer loose boxer shorts for running
• Runners who need heavy padding or compression shorts

Choosing the right running underwear comes down to fabric, fit, and seam construction. Prioritize moisture-wicking materials like Supplex®, a snug supportive fit, and flat or seamless design to avoid chafing. Use the decision rules above to match your run length, climate, and skin sensitivity. With the right pair, you'll forget you're wearing them—and focus on your run.