Semicrystalline polyolefins with narrow molecular weight distributions characterized by a low polydispersity index (PDI) and selected from the families of homopolymers, statistical copolymers, block copolymers, and graft copolymers, can be blended with a low molecular weight fluid diluent to create gel fiber and film compositions. These gel compositions, when subjected to mechanical or thermomechanical processing, either before or after removal of the diluent, result in fiber or film compositions that combine high tensile strength with other desirable physical properties, such as high rigidity, large extension at break, and/or high recoverable elasticity. These desirable combinations of properties are superior to those obtained from gel-processed semicrystalline polyolefins that are substantially similar in composition and molecular weight, but that have large PDIs.