Gait consistency test based on the impulse-momentum theorem

Abstract

The kinematic and dynamic aspects of human locomotion have been investigated during the last eighty years. Significant contributions were made towards the understanding of the mechanics of movement and of the joints. As a consequence the field of Rehabilitation and Orthopaedic Biomechanics advanced considerably. However the complexity of the kinematic and dynamic data of locomotion prevented the various techniques from becoming clinically applicable. This paper attempts to develop a technique for clinical evaluation of gait by relatively simple means. For this purpose the six components of the ground reaction forces were chosen for an analysis. The major tool of the technique is the time integral of the forces. Since this is a quantitative parameter with a distinct physical definition, it can be very meaningful as far as investment of efforts in ambulation is concerned. As a first step towards the reinforcement of this thesis a consistency test was developed. The consistency test ensures that the use of dynamic forceplates do not impose a bias on the test procedure. The test is meant to indicate whether the results are valid for further processing. The concept of the test is based on the fact that the velocity vector is expected to be equal in two equivalent points of consecutive walk cycles. It therefore follows that the time-force integral which equals the difference of momentum between the two points should be zero. The advantage of this test is that it does not discriminate between normal and pathological gait. The theory was tested with 28 subjects and the results have provided sufficient evidence for its verification.