Flexible strain sensors are key elements for many developing wearable electronic devices to monitor human activity. H. Here we are presenting an approach for the fabrication of strain-sensitive nanofiber threads utilizing an electrospinning process. A core-shell nanofibers, where a conductive core is automatically covered by an insulating layer, were produced from polyvinylidene fluoride as a base material and carbon nanotubes as a conductive filler. The nanocomposite core exhibits strong resistive strain-gauge response. We further demonstrate the possibility of incorporating the synthesized material onto fabric and utilizing a simple interface for detecting human movements. The presented technique of strain-sensitive material fabrication is simple and could be applied to many areas including the development of smart textile.