Author(s): LI, F., QIN, Z., VAN HOOREN, B., TROWELL, D., SHI, Y., Institution: SHANGHAI UNIVERSITY OF SPORT, Country: CHINA, Abstract-ID: 715

INTRODUCTION:
Temporal gait parameters, including contact time (CT), flight time (FT), and duty factor (DF), characterize running style and are associated with performance and musculoskeletal loading. Lower-limb strength, leg stiffness, and flexibility are recognized determinants of running mechanics, yet their integrated contributions and interaction pathways remain unclear, particularly whether strength influences gait timing directly or indirectly via stiffness modulation. This study quantified the associations of lower-limb maximal strength, leg stiffness (Kleg), and joint flexibility with temporal gait parameters, evaluated stiffness-mediated pathways linking strength to gait, and explored sex-specific interaction effects using multivariate regularized modelling.
METHODS:
Sixty-nine recreational runners (38 male, 31 female) completed three laboratory sessions assessing overground running biomechanics, isometric mid-thigh pull strength, and lower-limb joint range of motion. Temporal gait parameters and mass-normalized Kleg were obtained from markerless 3D motion capture during running at controlled speed. Peak force (PF) and rate of force development (RFD) were derived from force-platform IMTP testing. Elastic Net regression examined associations between neuromuscular variables and gait parameters while controlling for speed. Bootstrap mediation analyses tested indirect PF effects through Kleg.
RESULTS:
No sex differences were observed in CT, FT, or DF. Elastic Net models explained substantial variance (Partial R² = 0.447–0.515). Greater PF and Kleg were associated with shorter CT, longer FT, and lower DF, indicating a more aerial running pattern, while RFD showed no predictive relevance. Hip extension ROM predicted longer CT, with significant sex interactions demonstrating stronger flexibility–gait associations in males. Mediation analysis showed PF effects were largely indirect, with Kleg accounting for 49–63% of total associations with temporal gait parameters.
CONCLUSION:
Lower-limb strength, stiffness, and flexibility collectively explain a large proportion of variability in running temporal structure. The findings support a hierarchical neuromechanical model in which maximal force capacity influences gait behavior primarily through stiffness modulation rather than direct mechanical action. Sex-dependent flexibility effects indicate distinct regulation strategies between male and female runners. From an applied perspective, these results suggest that training interventions targeting stiffness development may more effectively alter gait timing than strength enhancement alone, and that flexibility modulation strategies should consider sex-specific responses. Overall, this work provides integrative mechanistic insight to inform individualized biomechanical optimization for performance and injury-risk management.