How to Choose Undies for Workouts: A Practical Buying Guide

Quick answer

For most workouts, choose a brief with full coverage and a soft elastic that holds it close, made from a breathable fibre like Tencel or organic cotton. Skip slick synthetic satin and loose cuts that ride up. If your main concern is chafing on long sessions, a high-leg or big-knicker cut with natural-rubber elastic is a reliable starting point.

Workout underwear has a harder job than everyday underwear. It has to stay in place through squats, sprints, and stretches, wick moisture instead of trapping it, and avoid seams or elastics that rub once you start sweating. Most discomfort people blame on leggings actually starts with the brief underneath.

This guide walks through the decisions that matter: cut, fabric, elastic, and fit. It uses real examples from our own range so you can see how those choices play out, and it flags where a different style might serve you better.

Start with cut, not fabric

Cut decides whether your underwear stays put. A brief with good coverage across the seat and a leg line that sits flat against the body is far less likely to ride up than a minimal cut. If you do a lot of floor work or hip-hinge movements, full-coverage styles hold their position better because there is more fabric anchored around the leg.

A high-leg cut is a useful middle ground. It is cut away at the front for freedom of movement but keeps a more traditional brief cut at the back, so it looks and feels secure. A traditional big-knicker shape gives the most coverage of all and suits people who want zero adjusting mid-session.

• Full coverage at the back = less riding up during squats and lunges.
• A flat leg line reduces friction under leggings.
• If you tug at your undies during warm-ups, the cut is wrong, not the size.

Choose a breathable fibre

Breathable workout underwear starts with the fibre. Tencel is a good pick for training because it is soft, silky, and moisture-friendly, which helps avoid the clammy feeling synthetics can create. Organic cotton is the other solid choice: it is breathable and gentle, and it handles sweat without turning slick.

What you want to avoid is a fabric that traps heat and holds odour. That is usually the plastic-based synthetics. If you are training hard and changing out of your kit straight after, a natural-fibre brief gives your skin a better environment than a polyester one.

• Tencel for a silky, cool feel under leggings.
• Organic cotton for classic breathability and everyday durability.
• Avoid slick synthetics if you sweat heavily or have sensitive skin.

Check the elastic and seams

Elastic is where workout underwear succeeds or fails. A soft elastic that holds the brief close without digging in is ideal. Natural rubber knitted into organic cotton is a common plastic-free option and tends to feel gentler against the skin than exposed synthetic elastic. Look for a waistband that sits flat, not one that rolls or pinches.

Seams matter too. Flat, low-profile seams are less likely to rub when you move. If a brief has bulky stitching at the leg opening, that is the spot that will chafe on a long run. Sewing thread is a small detail, but cellulose or tencel thread keeps the whole garment comfortable and consistent with a plastic-free choice.

• Soft leg elastic holds the brief close without pressure points.
• Flat seams reduce chafing under fitted leggings.
• Natural rubber and organic cotton elastic is a good plastic-free option.

Fit guidance for training days

Workout underwear should fit close but not tight. If the waistband leaves deep marks or you feel pressure across the hips, size up. If the brief shifts when you raise your arms or squat, it is too loose or the cut is wrong for your body. The right fit stays put through a full range of motion without you thinking about it.

Try your workout underwear on with the leggings or shorts you actually train in. Fabric on fabric behaves differently than fabric on skin. Do a few squats and a couple of lunges in front of a mirror. If nothing moves and nothing digs, you have your fit.

• Size up if the waistband leaves marks.
• Test with your real training bottoms, not just in front of a mirror in your everyday clothes.
• If you have to adjust it, return it or try a different cut.

Decision rules for workout undies

• If you do high-intensity or floor work: Choose a full-coverage brief with soft leg elastic, like Big Knickers - Black Tencel. The leg elastic holds the brief close so it does not ride up during squats or burpees. Coverage plus leg elastic is the safest combination for movement.
• If you chafe easily on long sessions: Look for a style with minimal or no leg elastic, such as The Very Good Undies - Rum & Raisin - 3 Pack, which has elastic only in the waist. Fewer contact points mean less friction. Less elastic at the leg opening can mean less rubbing.
• If you want freedom at the front and coverage at the back: Try High-Leg Briefs. The cut-away front allows a full range of motion while the traditional back keeps coverage secure. A high-leg cut balances mobility and security.
• If you sweat heavily or have sensitive skin: Skip plastic-based synthetics. Choose Tencel or organic cotton, which breathe and do not trap heat the way polyester can. Natural fibres are the better base layer for sweaty training.

How our styles compare for workouts

• Big Knickers - Black Tencel: Made in premium Lenzing tencel, knitted and dyed in Australia, with soft leg elastic to hold them close and Cradle to Cradle Gold certified Vinatur elastic. The leg elastic keeps the brief in place during movement, and the tencel fibre is breathable and soft, which suits sweaty sessions.
• High-Leg Briefs: Cut away at the front with a more traditional brief cut at the back, made in premium organic cotton with natural rubber and organic cotton elastic. The high-leg shape gives freedom of movement at the front while the back coverage reduces riding up, and the natural-rubber elastic is a plastic-free option that feels gentle on skin.
• The Very Good Undies - Rum & Raisin - 3 Pack: A classic boy-leg brief with elastic only in the waist, made in premium Lenzing Tencel with organic cotton and natural rubber elastic. Elastic only at the waist means no leg elastic to rub, which can suit people who chafe easily, though the looser leg line may shift more during high-intensity movement.

Who these picks suit

Best for

• People who want underwear that stays put during gym sessions, runs, or yoga
• Anyone prioritising breathable, plastic-free fibres for exercise
• Those who chafe easily and want minimal elastic at the leg

Not for

• Anyone needing high-compression or padded athletic support, which these styles do not provide
• People who prefer a thong or g-string for workouts
• Those who want a seamless, laser-cut synthetic brief specifically

The right workout underwear comes down to cut, fibre, and fit. Choose a style that covers well, breathes, and holds its shape through movement, then test it with the leggings you actually train in. If you want a plastic-free starting point, our Tencel and organic cotton briefs are built for exactly that.