This study was designed to explore the impacts of increased longitudinal bending stiffness (LBS) on running economy (RE) and running biomechanics. A systematic search across four electronic databases (MEDLINE, Web of Science, EBSCO Host, Scopus) was performed on 1 March 2025. Twenty-three studies that fulfilled the inclusion criteria were selected. The Cochrane Risk of Bias Assessment Tool was used to evaluate the methodological quality of the included studies. Stata 18 was used for statistical analysis of the included indicators, including Ankle peak moment (APM), metatarsophalangeal range of motion (MTP ROM), and contact time. Subgroup analyses were carried out to evaluate the potential impacts of moderator variables (Runner level and Gradient of LBS) on the main outcome variable. Compared to non-increased LBS, increased LBS enhanced RE (SMD =-0.28 95% CI -0.39, -0.17, Z = -5.112, p < 0.001). Significant increases in APM (SMD = 0.23,95% CI 0.08, 0.53, Z = 2.84, p = 0.003), MTP ROM (SMD = 0.33,95% CI 0.15, 0.41, Z = 2.54, p = 0.002), and contact time (SMD = -0.17,95% CI0.09, 0.35, Z =-2.32, p = 0.02) were observed when LBS was increased. In subgroup analyses, elite runners showed a significantly greater improvement in RE (VO2 reduction of 4.2%) than recreational runners (1.5%). RE was significantly improved (VO₂ reduction of ≥ 3%) only when LBS was ≥ 8 Nm/rad, while no significant difference was found between the low LBS group (≤ 5 Nm/rad) and the control group. Conclusions/Discussion: Increased LBS has a positive impact on RE and certain aspects of running biomechanics. The extent of improvement in RE may be influenced by factors such as the runner's level and the gradient of LBS. Future research is needed to explore the optimal levels of LBS for different types of runners and running conditions to enhance running performance.
Jiang et al. (Thu,) studied this question.