Date of Award

7-2001

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Health, Physical Education and Recreation

First Advisor

Dr. Nick Stergiou

Second Advisor

Dr. Blanke

Third Advisor

Dr. Stuberg

Fourth Advisor

Mr. Paladino

Abstract

Running has been associated with a number of lower extremity overuse injuries. Attention has been given to biomechanical factors, specifically, excessive pronation and excessive tibial rotation. It has been suggested that excessive tibial rotation is due to excessive foot pronation transferred through a coupling mechanism. The ankle and knee are mechanically linked via the tibia and excessive tibial internal rotation may delay tibial external rotation as the knee begins to extend. Increased impact forces have also been implicated as a cause of running injuries, although little is known about this possible relationship. Obstacle heights have been used previously to produce increases in impact forces. Investigation of biomechanical factors has traditionally been two-dimensional. However, recent literature has shown limitation to two-dimensional analysis. Therefore, the purpose of this study was to investigate the coupling mechanism between the subtalar and knee joints during running over obstacles of varying heights using a three-dimensional analysis.

Ten, heel strike subjects ran at a self-selected pace under a no obstacle condition and four obstacle conditions (5, 7.5, 10, & 12.5% of standing height) on day 1 and underwent an orthopedic exam on day 2. The obstacle was placed directly before a force platform (960 Hz). Videography was collected using two high-speed cameras (240 Hz). Seven reflective markers were placed on the right limb to identify a three-dimensional 3-segment model.

Increasing obstacle height resulted in increased impact forces. This allowed examination of the coupling mechanism over a spectrum of various impact force magnitudes. The pronation curve transitioned from a unimodal to a bimodal configuration and the bimodal tibial rotation curve experienced increases in the bimodal characteristics. Increasing impact forces resulted in increases of maximum pronation and maximum tibial internal rotation as well as decreasing the time to reach maximum knee flexion. However, the times to maximum pronation or maximum tibial rotation remained unaffected. This resulted in increases in the time differences between maximum pronation and maximum knee flexion. Therefore, the tibia may have been put under abnormal torsional stresses that were augmented with increasing impact forces as the proximal end began external rotation due to earlier knee flexion and the distal end maintained internal rotation due to unchanging pronation times. Future studies will focus in the measurement of these forces, as well as to justify these phenomena with additional perturbations.

Comments

A Thesis Presented to the School of Health, Physical Education, and Recreation an the Faculty of the Graduate College at the University of Nebraska In Partial Fulfillment of the Requirements for the degree Master of Science University of Nebraska at Omaha. Copyright 2001 Tracy Allan Dierks.

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