The mechanics of sprint running performance: Why getting even doesn’t help, but footwear can

Prajapati, Sunil Kishor

Item

The mechanics of sprint running performance: Why getting even doesn’t help, but footwear can

Prajapati, Sunil Kishor

Date

2025-05-05

Abstract

Introduction: Sprint running performance is determined by ground force application and limited by fatigue. Although these phenomena are generally appreciated, how sequential steps and individual limb mechanics might account for them is not well understood. This dissertation investigates three key aspects of sprint running performance: (1) the effects of footwear on maximal sprinting speed and speed endurance, (2) the relationship between bilateral symmetry and sprinting performance, and (3) the gait and sprint performance consequences of an acutely introduced limb length asymmetry. Together, these studies aim to advance our understanding of the biomechanical determinants of sprinting performance. Methods: Three experimental studies were conducted. Study 1 tested whether prototype footwear, designed with increased bending stiffness and a thicker, more cushioned midsole than conventional footwear, could improve overground sprinting performance in 15 athletes during 60 m, 100 m, and 130 m sprints. Step kinematics and ground force application were analyzed using radar, accelerometers, and high-speed video. Study 2 examined the symmetry of individual limb ground force application during high-speed treadmill running among 16 athletes, including sprinters, athlete non-sprinters, and sprinters with known anatomical asymmetries, running on a force-instrumented treadmill at speeds ranging from 60% to 100% of their maximum. Study 3 evaluated whether an acute, unilateral limb-length perturbation (2.5 cm elongation of one shoe) affected gait mechanics and maximal sprinting speed in 12 athletes, assessed through progressive treadmill tests to failure. Results: The prototype footwear in Study 1 increased maximal speed (+2.3%), lengthened steps (+1.6–1.9%), and improved sprint endurance, with performance benefits tending to be larger at longer distances (e.g., +2.7% in the final 30 m of 130 m sprints). Study 2 revealed that faster sprinters exhibited greater between-limb asymmetries in stance-averaged force (7.90±3.5% vs. 5.30±2.8%, p<0.01) and impulse (10.5±4.7% vs. 7.6±3.9%, p<0.01) compared to non-sprinters, while anatomically asymmetrical sprinters (n=4) displayed significantly greater between-limb force application asymmetries than the competitive sprint and athlete, non-sprint groups. Study 3 demonstrated that an acute single-limb elongation intervention did not impair maximal speed (8.12±1.49 vs. 8.18±1.46 m/s), because runners adapted by redistributing between limbs forces to meet the gait requirements and thereby conserve maximal running speeds. Conclusion: These findings indicate that: 1) sprint performance can be enhanced by footwear interventions that improve bilateral force application and reduce the fatigue particularly during longer sprints, 2) bilaterally symmetrical ground force application is not a prerequisite for achieving fast sprint running speeds, and 3) fast speeds ca be attained with both natural and induced asymmetries due to compensatory between-limb gait adaptations.