A fiber comprising (a) from 40 wt% to 98 wt% of a low crystallinity polymer and (b) from 2 wt% to 60 wt% of a high crystallinity polymer, said wt% values being with respect to the total weight of said high- and low crystallinity polymers, wherein said fiber is capable of undergoing plastic deformation upon elongation, and wherein said low crystallinity polymer comprises at least one ethylene/α-olefin interpolymer, wherein the ethylene/α-olefin interpolymer is a block copolymer comprising at least 60 mole percent ethylene and satisfies one or more of the following criteria: (a) has a Mw/Mn from 1.7 to 3.5, at least one melting point, Tm, in °C (degrees Celsius), and a density, d, in g/cm 3 (grams/cubic centimeter), wherein the numerical values of Tm and d correspond to the relationship: Tm > − 2002.9 + 4538.5 d − 2422.2 d 2; (b) has a Mw/Mn from 1.7 to 3.5, and is characterized by a heat of fusion, ΔH in J/g, and a delta quantity, ΔT, in °C (degrees Celsius) defined as the temperature difference between the tallest DSC peak and the tallest CRYSTAF peak, wherein the numerical values of ΔT and ΔH have the following relationships: Δ T > − 0.1299 ΔH + 62.81 for ΔH greater than zero and up to 130 J/g, ΔT > 48°C for ΔH greater than 130 J/g, wherein the CRYSTAF peak is determined using at least 5 percent of the cumulative polymer, and if less than 5 percent of the polymer has an identifiable CRYSTAF peak, then the CRYSTAF temperature is 30°C; (c) is characterized by an elastic recovery, Re, in percent at 300 percent strain and 1 cycle measured with a compression-molded film of the ethylene/α-olefin interpolymer, and has a density, d, in g/cm 3 (grams/cubic centimeter), wherein the numerical values of Re and d satisfy the following relationship when ethylene/α-olefin interpolymer is substantially free of a cross-linked phase: Re > 1481 − 1629 d; (d) has a comonomer content of a TREF fraction which elutes between 40°C and 130°C greater than or equal to the quantity (-0.2013)T + 21.07, wherein T is the numerical value of the peak elution temperature measured in °C; (e) an average block index greater than zero and up to 1.0 and a molecular weight distribution, Mw/Mn, greater than 1.3;and (f) at least one molecular fraction which elutes between 40°C and 130°C when fractionated using TREF, characterized in that the fraction has a block index of at least 0.5 and up to 1. (a) has a Mw/Mn from 1.7 to 3.5, at least one melting point, Tm, in °C (degrees Celsius), and a density, d, in g/cm 3 (grams/cubic centimeter), wherein the numerical values of Tm and d correspond to the relationship: Tm > − 2002.9 + 4538.5 d − 2422.2 d 2; (b) has a Mw/Mn from 1.7 to 3.5, and is characterized by a heat of fusion, ΔH in J/g, and a delta quantity, ΔT, in °C (degrees Celsius) defined as the temperature difference between the tallest DSC peak and the tallest CRYSTAF peak, wherein the numerical values of ΔT and ΔH have the following relationships: Δ T > − 0.1299 ΔH + 62.81 for ΔH greater than zero and up to 130 J/g, ΔT > 48°C for ΔH greater than 130 J/g, wherein the CRYSTAF peak is determined using at least 5 percent of the cumulative polymer, and if less than 5 percent of the polymer has an identifiable CRYSTAF peak, then the CRYSTAF temperature is 30°C; (c) is characterized by an elastic recovery, Re, in percent at 300 percent strain and 1 cycle measured with a compression-molded film of the ethylene/α-olefin interpolymer, and has a density, d, in g/cm 3 (grams/cubic centimeter), wherein the numerical values of Re and d satisfy the following relationship when ethylene/α-olefin interpolymer is substantially free of a cross-linked phase: Re > 1481 − 1629 d; (d) has a comonomer content of a TREF fraction which elutes between 40°C and 130°C greater than or equal to the quantity (-0.2013)T + 21.07, wherein T is the numerical value of the peak elution temperature measured in °C; (e) an average block index greater than zero and up to 1.0 and a molecular weight distribution, Mw/Mn, greater than 1.3;and (f) at least one molecular fraction which elutes between 40°C and 130°C when fractionated using TREF, characterized in that the fraction has a block index of at least 0.5 and up to 1.