Using stretch stitch on sewing machine, you can create stretchy fabric cable.
The picture shows 9 line stretchy fabric cable, which resistance is 150 ohm/m.

In most applications it is important to isolate the conductive traces. For stretchy traces this requires a stretchy isolation. So far we have experimented and had good results with: stretchy fabric glue, puffy fabric paint and extra layers of fabric.

Stretchy conductive traces are great for wearables because their stretchiness makes these traces comfortable and durable against wear and strain.

Non-stretchy traces make very stable connections on a non-stretch fabric but make less or no sense when working with stretchy fabrics.