The Workout Thong - Black

Key Benefits

• Engineered for gym leggings.

• Wicks moisture to stay dry.

• Four-way stretch for flexibility.

• Extra-long antimicrobial gusset.

The Workout Thong pairs technical performance with total comfort—engineered specifically to stay put under gym leggings. Made from recycled nylon with built-in sweat-wicking technology, it dries quickly to keep the skin dry, fresh, and irritation-free while you move.

The four-way stretch offers unrestricted flexibility and shape retention, allowing the thong to adapt to the body and hold its fit through high-impact workouts and daily wear. With minimal visible lines and functional seams that resist bunching or rolling, it delivers confidence and comfort during every squat, stretch, or sprint.

The extended gusset features antimicrobial properties to support skin health, while the contrast stitch detail adds a sleek, modern touch. The Workout Thong is OEKO-TEX® certified, ensuring all materials are clean, non-toxic, and safe for sensitive skin.

Underdays uses breathable fabrics that feel soft against the skin and adapt to your every move. Each piece carries the OEKO-TEX® certification, meaning it has been tested for harmful substances and proven safe for direct contact with your body. The fabrics offer all-day comfort without irritation, making them ideal for both busy routines and moments of rest.

Underdays was founded in December 2021 by Oria Mackenzie & Amelie Salas with a mission to reimagine underwear as a form of everyday self-care. Inspired by the idea that underwear should feel as good as it looks, the founders set out to create pieces that combine style, comfort, and performance. Each design is developed in collaboration with a gynaecologist to support women through daily routines, active moments, and everything in between. By focusing on breathable fabrics and thoughtful fits, Underdays empowers you to feel confident, supported, and comfortable every single day.

With our Healf Curation Process, we do the work for you. Shop with confidence knowing that every item has been tried, tested, and curated for you.

Learn more about each step—Brand Discovery, Expert Validation, and Community Testing—here.

Material:
Fabric: 80% Recycled Nylon, 20% Elastane Lycra
Gusset: 47% Modal, 46% Cotton, 7% Spandex

All fabrics are OEKO-TEX certified (BEKO 108840 Testex)

Shipping

At Healf, we prioritize safe and fast delivery for all our customers. Our carefully selected couriers are Royal Mail and DPD.

UK standard delivery

Enjoy free standard delivery on orders above £50, this option usually requires 2-3 working days. If your order is under £50, this delivery option is available for £3.99.

Next working day

For when you need our products urgently, we offer next working day shipping for £5.99. For orders placed before 12.00, we will ship it the same day to ensure you receive your order the next working day.

International

International deliveries can take 7 working days, and up to 4 weeks. The cost is £22.99 for orders below £50, £49.95 for orders above.

Returns

If for any reason you are not satisfied with your order, we provide free 365-day UK returns for all our customers. To initiate your return, simply contact us at team@healf.com, and we'll send you a return slip and help arrange a collection. The item you return must be sent in the same condition as received and inside the original packaging. Once received, we will notify you via email.

For international returns, we unfortunately do not cover the cost. However, we work with an array of carriers and can offer self-posting returns for customers shopping from outside the UK.

Care:
Cool wash, 40° max.
Air-dry flat in a shaded area.
Do not iron or tumble dry.