Date of Award


Document Type

Honors Thesis

Degree Name

Bachelor of Arts



Advisor/Committee Chair

John Polk


During running, the limb acts as a mechanical spring where it compresses and recoils to release elastic potential energy with each ground contact. Maintaining maximal running speed is particularly important during sprinting. Individuals with stiffer limb springs are more efficient because of this. Limb stiffness can be calculated using Hooke’s law (k=F/ ΔL), where k is the spring constant, F is the peak ground reaction force, and ΔL is the change in hip height between the initiation of limb contact and the middle stance phase. Many factors contribute to limb stiffness and this study examines how stiffness variers with contact as well as how it's affected by body size. The extent to which knee and ankle flexion contribute to the changes in limb length will also be looked at. The study included nine elite college sprinters from the University of Illinois who hopped in place at different frequencies. Kinematic data and peak ground reaction forces were collected and analyzed. The results collected suggested that ­­­­stiffness of ankle and knee angles varied with increasing frequency. The ankle exhibits greater compliance due to its adaptive nature and is the site of the highest elastic potential energy source and exhibited lower stiffness.