Biomechanical analysis of transfemoral amputee's sprint running and block start

Abstract

Ojala, Paula Emilia, 2012. Biomechanical analysis of transfemoral amputee’s sprint running and block start. Department of Biology of Physical Activity, University of Jyväskylä, Master’s Thesis in Biomechanics. 87 p.

Although a large number of studies about human locomotion have been reported, little is known about how to run with a prosthesis limb. The purpose of the study was to examine the difference between the healthy and prosthesis leg and between different prostheses during the sprint start and maximal running speed. One top level male sprint runner (100 m personal best 13.11 s) with the unilateral transfemoral prosthesis participated in this study. Two specific sprint prostheses (A: mass = 2.3 kg and B: mass = 2.7 kg) were used. Ground reaction forces (GRF) were recorded together with high-speed video recordings that were used for three-dimensional analysis. The first six steps from the sprint start and a step cycle at the maximal speed were measured for both healthy and prosthesis legs.

The highest running speed measured was 7.45 m/s, which was acquired by prosthesis A, although the differences between prostheses in measured parameters were minor. The results showed great asymmetry between the healthy and the prosthesis legs. The knee joint kinematics of the prosthesis leg differed from the sound limb as the prosthesis leg must land with the knee joint fully extended. The upper body was bent backwards and the prosthesis hip extended to assist in landing with the straightened leg causing a shorter step length on the prosthesis leg. The main compensation method for the subject to be able to run was to adjust the swing time to contact times of each step cycle making the step cycle time constant. Horizontal and vertical GRF during impact and push-off phase were smaller for prosthesis than for the sound leg as a consequence of the lack of force producing muscles and limited prosthesis properties. The length of the prosthesis was too long and caused a sideways swing of the prosthesis. As a solution the prosthesis length was shortened and the subject was advised to do strength training to achieve a fore foot contact on the sound side. In addition to these on an upright body posture was suggested to improve the running technique of the subject. A few months later the subject made his new record with a 0.26 s improvement.