The fabric stretches over the course of the day

Short answer: Viscose fibres give when they get warm and damp. Choose a quality with a little elastane and let the garment rest for a day so the shape returns.

Why it happens

Bamboo viscose is a soft fibre that absorbs moisture. When body heat and sweat make the fabric warm and damp, the fibres slide slightly against each other and the garment grows longer and wider. It shows most at knees, elbows and seat where there is most movement.

How much is normal

A couple of centimetres over a day is ordinary in thin fabric without elastane. More than that suggests a loosely knitted quality, or a size that was too big to begin with. A little elastane in the blend holds the shape far better.

How to get the shape back

Lay the garment flat for a day so the fibres settle. A wash at thirty degrees and flat drying puts it fully back. Do not hang heavy wet garments on a hanger, because the weight pulls the fabric exactly when it is softest. See bamboo leggings.

Choose right from the start

For clothes you wear all day, pick a quality with elastane and a size that sits close without pinching. For nightwear and loungewear the stretch matters far less. See loungewear for women and bamboo trousers for women.

Frequently asked questions

Does the stretch always come back

In fresh fabric yes. After many washes and much wear some of it becomes permanent.

Does washing cold help

Yes. Heat and a hard spin pull hardest on the fibres and make the stretch permanent.

Should I buy a size smaller

No, not as a fix. Choose a quality with elastane in your normal size instead.