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The Workout Thong - Black
A fast-drying, squat-proof thong with four-way stretch, designed to stay put under gym leggings and move with you.
In stock. Next day delivery available.
Healf Zone members get free next day delivery on all orders.
Buy now, pay later from £4.50/mo
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)
Care:
Cool wash, 40° max.
Air-dry flat in a shaded area.
Do not iron or tumble dry.
The Workout Thong - Black
A fast-drying, squat-proof thong with four-way stretch, designed to stay put under gym leggings and move with you.
In stock. Next day delivery available.
Healf Zone members get free next day delivery on all orders.
Buy now, pay later from £4.50/mo
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)
Care:
Cool wash, 40° max.
Air-dry flat in a shaded area.
Do not iron or tumble dry.
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Frequently asked questions
Every product undergoes our Healf Curation Process. With it, you can shop confidently knowing that every item has been tried and tested before it reaches you. Our Healf Curation Process includes three key steps: Brand Discovery, Expert Validation, and Community Testing. Through these, we assess quality, ingredients, effectiveness, and more, ensuring that every product empowers your wellbeing.
The Healf Source offers detailed insights into different aspects of wellbeing, as well as guidance, research, recipes, and more to help you invest in your personal wellbeing journey. You can also subscribe to our weekly newsletters for the latest updates at Healf and in the wellbeing industry. Subscribe via the sign-up block at the bottom of this page.
We love people who check ingredients as carefully as we do, so you'll find detailed information about the ingredients used on every product page (where applicable). If you see something you'd like to flag with us or have additional questions, please don't hesitate to get in touch—we'd love to hear from you.
Healf Curation Process™
Every product undergoes our rigorous Healf Curation Process, ensuring you are always getting the best when it comes to your wellbeing.
The Discovery
Expert Validation
Community Testing
The Discovery
Expert Validation