Abstract: Flexible wearable mechanical sensors hold broad application prospects in sports training monitoring. However, trade-offs between sensitivity and detection range, as well as issues regarding signal stability and motion artifact interference, continue to restrict their practical application. Addressing the actual needs of sports training, this paper systematically reviews research progress in flexible sensors, focusing on three key dimensions: dynamic response under large deformation, sweat resistance and wearing comfort, and real-time feedback with system integration. Typical strategies, including liquid metal utilization, island-bridge structures, microcrack control, and ion-electron cooperative transmission, are analyzed in detail. Furthermore, shortcomings in current research concerning action quality evaluation, individual difference calibration, and model interpretability are identified. On this basis, this paper constructs a sensor performance evaluation framework and clarifies three core bottlenecks: sweat resistance and permeability, dynamic signal stability under high-frequency impact, and the transformation from data to decision-making. Finally, future development directions are prospected, including multi-physical field cooperative regulation, signal decoupling and intelligent algorithm fusion, self-powered system integration, and long-term biocompatibility, aiming to provide a theoretical reference for the design of high-performance flexible sensors for sports training.