Fiber-based strain sensors have emerged as revolutionary components in flexible electronics owing to their intrinsic compliance and textile compatibility, particularly in human-centric applications ranging from health diagnostics to motion tracking. While substantial progress has been achieved, a critical challenge persists in reconciling the contradictory demands of ultrahigh sensitivity and stable signal transmission through rational structural design. Herein, we develop dual-structure silver (Ag)/polyurethane (PU) fiber-based strain sensors (Ag@PU_x) via an integrated wet spinning and interfacial metal ion deposition (IMID) strategy. Notably, we propose a mechanical pre-stretching strategy that enables precise regulation of strain sensitivity and sensing range through controlled substrate deformation. Systematic characterization reveals that pre-stretched PU fibers form ordered microscale conductive networks, exhibiting exceptional electrical stability (conductivity (σ) = 1.9 × 10⁵ S·m⁻¹; the change in resistance value under external tensile force (ΔR)/the initial resistance of the sensor (R₀) < 0.03 under 360° torsional deformation) with a high quality factor (Q) of 10.1 at 50% strain. In contrast, non-prestretched counterparts develop microcrack-dominated architectures, achieving a high sensitivity (gauge factor (GF) = 7.7) through strain-induced crack propagation and a fracture strain exceeding 660%. A systematic investigation elucidates the underlying mechanisms behind these distinct sensing performances. The Ag@PU_x fiber-based electronics are capable of adapting to various tasks including human motion monitoring, voice recognition, and gesture recognition. Importantly, we developed the Ag@PU_x fiber-based electronics to monitor motion states while stably transmitting electrical signals. Ultimately, the Ag@PU_x show great promise in applications such as motion monitoring, waist rehabilitation, thermal management, electromagnetic shielding, and antibacterial deodorization.