An extensible implantable electrical lead includes a lead body having a proximal region and a distal region. The lead body is formed of a polymeric material that is extensible between a first length and a second length. A first plurality of electrical conductors are disposed within the lead body and extend between the proximal region and the distal region. The first plurality of electrical conductors are each electrically insulated and spaced apart from each other and form a side-by-side co-planar first sigmoidal pattern between the proximal region and the distal region.