Physiotherapy - Theses
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ItemKnee motion and foot speed at and around initial contact in human gait( 2014)Biomechanical analyses have provided detailed information about joint kinematics and kinetics of the gait cycle. Interpretation of this data has largely overlooked (Winter, 1983a), or even misrepresented (Cerny, 1984; Perry, 1992), knee kinematics around initial contact (IC). It has been suggested that heel speed (HS) approaches zero magnitude as a way of preparing the foot for landing at IC and that knee kinematics influence this event (Winter, 1992b). A number of factors, including the re-introduction of ground reaction forces to the leading limb, make IC a complex event within the gait cycle. The aim of this study was to clarify knee joint kinematics at and around IC in human gait. Three hypotheses were tested. Firstly, that knee flexion (KF) precedes IC. Secondly, that the quantum of knee flexion and the percentage of stride spent flexing the knee prior to initial contact are dependent on gait speed. And thirdly, that HS is reduced to near zero magnitude in preparation for contact with the ground at the start of stance phase. Sixteen healthy, young adults participated in this study. A Vicon 3D Infra-red motion analysis system (Oxford Metrics Ltd., Oxford, England) sampling at 120 Hz and AMTI Force Plates (Advanced Mechanical Technology, Inc., Watertown, USA) sampling at 1080 Hz were used to record kinematic and kinetic data from walking trials at each of three self-selected speeds: slow; preferred and fast. Data were extracted representing the timing of the onset of KF prior to IC, the amount of KF occurring between maximum knee extension prior to IC and IC as well as HS at IC. The data were assessed for normality using the Kolmogorov-Smirnov test of normality and through skewness and kurtosis. Friedman’s χ2r statistic and RM MANOVAs were used to investigate differences across gait speed. Post hoc testing was performed with the Wilcoxon test and contrasts testing. KF data were found to be non-normal. At preferred speed 2.6% of stride was taken up flexing the swinging knee 1.4° prior to IC. This rose to 3.5% of stride and 2.3° of flexion prior to IC at fast speed and fell to 2.2% of stride and 0.8° of flexion prior to IC at slow speed. The quantum of KF prior to IC also increased with gait speed. All HS data were normal. Mean HS at IC was 559.7mm•s-1 at preferred speed. Mean HS at IC rose to 841.3 mm•s-1 at fast speed and fell to 391.2 mm•s-1 at slow speed. KF and HS were found to be significantly different across speeds (p < 0.001). Results support the hypothesis that KF occurs prior to IC in human gait. The amount and duration of this KF were dependent upon walking speed. These findings suggest that in human gait a motor control strategy is implemented where the knee flexes in anticipation of initial contact. This repudiates the common perception in the gait literature that the knee is extended, or stable in extension at IC (eg Gage, 1990; Cerny, 1984). Whilst HS does slow late in swing the results of this study do not support the proposition that a function of knee motion prior to IC is to reduce HS to near zero magnitude. The outcomes of this study provide clinicians with crucial information to guide decision making with respect to gait analysis and training.