Objective This study systematically evaluates the effects of longitudinal bending stiffness (LBS) of running shoes on running economy and athletic performance. Literature published between 1995 and 2025 was retrieved from CNKI, PubMed, Web of Science, and Elsevier databases. The objective is to quantify the effectiveness of LBS adjustments under different running conditions and to identify how plate geometries and placement configurations regulate the mechanical response of the shoe-foot system. The findings provide scientific evidence for the engineering optimization and individualized design of running footwear.

Analysis A total of 31 studies satisfied the inclusion criteria. Of these, 15 investigations (48.4%) reported positive outcomes resulting from increased LBS, mainly reflected in reduced metabolic cost or improved performance metrics. Another 15 studies (48.4%) reported no statistically significant differences, while 1 study (3.2%) identified performance degradation. Among 10 sprint-focused studies, seven studies (70%) indicated that higher LBS contributed to improved performance, primarily manifested as reductions in sprint completion time. These results demonstrate that increased bending rigidity can improve mechanical energy transfer and propulsion efficiency in short-duration, high-power running tasks. Endurance-running outcomes exhibit higher variability. Under anaerobic threshold (AT) conditions (n =11), only three studies (27.3%) documented performance or metabolic benefits, while the majority reported no significant differences. This suggests that the mechanical contribution of LBS may be constrained when runners operate near physiological limits. Under fixed-speed running scenarios (n =10), however, five studies (50%) reported improved running economy, indicating that LBS is more effective when the mechanical workload is stable and not dominated by metabolic saturation effects. Differences in LBS modification strategies significantly influenced outcomes. Among 11 studies utilizing flat plate structures, only two observed positive effects, whereas five of six studies incorporating curved plates showed improvements. The superiority of curved plates is attributed to their enhanced conformity to metatarsophalangeal (MTP) joint kinematics and improved bending-axis alignment. Plate insertion configurations can be grouped into four engineering layouts: beneath the insole, embedded in the midsole, positioned between the midsole and outsole, and located beneath the outsole. Midsole-embedded plates demonstrated the highest rate of positive outcomes (71.4%), confirming that mechanical integration within the midsole is critical for effectively altering the composite bending stiffness of the shoe. Plates placed beneath the insole showed moderate effectiveness (33.3%), while the other two configurations lacked sufficient evidence and produced inconsistent results, indicating suboptimal structural coupling. Mechanistic evidence shows that appropriate increases in LBS reduce negative work and increase positive work at the MTP joint. These changes modify the mechanical leverage of both the ankle and MTP joints during propulsion, resulting in improved energy return and reduced metabolic cost. From an engineering biomechanics perspective, LBS adjustments influence the load distribution pathway, bending axis position, and timing of joint work redistribution across the lower limb. However, user-specific factors significantly affect the system-level response. Studies suggest that each runner may exhibit an individualized “optimal stiffness”, determined by variables such as foot morphology, tendon elasticity, running technique, and muscular strength. Deviations from this optimal range can introduce inefficiencies or increase metabolic cost, underscoring the necessity for personalized stiffness calibration in footwear engineering.

Conclusion In summary, the appropriate LBS configuration can provide measurable benefits in running performance, particularly in sprint applications and fixed-speed endurance running. The performance gains arise from enhanced mechanical energy storage and return, improved leverage mechanics, and optimized joint work distribution. Future engineering research should prioritize stiffness-adaptive designs, integration of curved plate geometries, and individualized stiffness matching to balance performance enhancement with safety and user-specific requirements.