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The first synthetic-blend running shirt that biodegrades like a 100% cotton tee, our Runterra Bio offers the enhanced moisture and odor control of specially-formulated 37.5® polyester with the comfort and versatility of cotton. This new, innovative fabric breaks down into organic compounds significantly faster than conventional polyester which takes over four hundred years.
Don’t sweat it — this tee will only start to biodegrade in anaerobic (oxygen-poor) environments. It breaks down in the landfill, not in your closet. Read more
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features
Biodegradable
Runterra Bio is powered by a specially formulated 37.5® polyester with enhanced biodegradation to break down into bio-based compounds significantly faster than conventional synthetics in an oxygen-poor environment like a landfill
Premium cotton
Made from long staple, US-grown Supima® cotton for superior softness, strength + durability
Active comfort
37.5® polyester with embedded volcanic ash provides enhanced heat + moisture regulation as well as odor-resistance
New sport raglan
Signature raglan sleeve design keeps seams off the top of the shoulders for comfort
Hang it up
An elastic locker loop is integrated into the back neck tape
materials + specs
Runterra |
Weight Garment made in Vietnam |
Fabric Callout

Runterra
Lightweight, resilient, and versatile, Runterra wears like your softest cotton tee with the added benefits of active odor-resistance and thermoregulation — thanks to volcanic particles embedded within the fabric.
SHOP ALL RUNTERRAcare instructions
Wash cold with like colors Machine dry low or hang dry for best results and lifespan of the garment |
Heads up — Runterra is not pre-shrunk We have relaxed the body and slightly lengthened the sleeves of this top to accommodate for some shrinkage which may occur in the wash cycle since Runterra is made from a majority natural fiber. Avoid washing and drying with high heat. |
sustainability
Why do biodegradable synthetics matter?
While we design Janji gear to last and hold up to the demand of years of running, no tee or running shorts should last forever. With this in mind, we are researching innovative ways to improve end-of-life cycle management of our apparel. While we look into longer-term solutions and circular methods — recycle, repurpose and reuse programs — we also know that most textiles are thrown out and end up in landfills. Conventional synthetics, used heavily in active apparel for their high-performance functionality, do not biodegrade in typical landfill conditions. This includes synthetics made from recycled materials, and is why most plastic seemingly lasts forever.
We are seeking solutions to fix this as a performance apparel company that relies on synthetics, including the use of non-ecotoxic biodegradability within our textiles like this new Runterra Bio. This is the first step on a better path forward.
Runterra is made from premium, long-staple Supima® cotton which is 50% longer and up to 45% stronger than other cottons (and softer, too). The stronger the fiber, the more durable the garment, and therefore the more it can be worn. Supima® cotton is grown by a select few family farms that utilize advanced water and soil management techniques to reduce consumption and ensure the health of the land for optimal renewability.
Runterra fabric is also OEKO-TEX® certified, meaning it is free from harmful chemicals and is fabricated in a way that meets a high environmental standard.
Learn more about our sustainable initiatives here.

JOIN THE COLLECTIVE
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Janji Collective Membership
£25
Key member benefits:
- 15% lifetime discount.
- Priority access to all releases.
- Limited run Janji gear.
Janji Collective Membership
Key member benefits:
- 15% lifetime discount.
- Priority access to all releases.
- Limited run Janji gear.
The £25 membership fee goes toward supporting clean water initiatives through our clean water partner
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