Introduction: The gait of older adults is characterized by such gait parameters as slow walking velocity and small range of change in joint angle. The effect of aging on these parameters has been analyzed independently, but the strength of the aging effect on each parameter has not been determined in detail. In the present study, using principal component analysis and analysis of variance, we clarified the strength of the aging effect on gait parameters. Method: The participants were 616 older adults (65 to 91 years old) living in Nangai Village located in northern Japan and 45 young adults (20 to 39 years old). The participants were classified by gender and into five age groups (aged 20 to 39 years, 65 to 69 years, 70 to 74 years, 75 to 79 years, and 80 years or above). They walked on an 11-meter straight walkway at their preferred speeds. The coordinates of markers attached to participants' iliac spines, knees, ankles, toes, and heels were measured using a Vicon-370 system (Oxford Metrics, Oxford, England) during 5 meters near the middle of the walkway. The sampling frequency was 60 Hz. From this three-dimensional data, we calculated 34 representative gait parameters. For these parameters, through principal component analysis and two-way analysis of variance by gender and age groups, we determined aging-related principal components and parameters belonging to each component. Results and Discussion: Through principal component analysis, we detected ten components with over one point of eigen value. After two-way analysis of variance for component score, we classified components according to whether they were age-related or not. The age-related components were the first principal component, with 26.0% of contribution rate. In the first component, stride length, toe height on heel contact, peak extension angle around the hip joint, and magnitude of vertical sway had a high component score; we labeled this component the "stride length" component. The parameters of cadence, single stance time, and magnitude of lateral sway had a high score in the second component (11.0% of contribution rate), which we labeled the "stride duration" component. In the second component, we detected significant gender difference. Components with less than 5% explanation of variance were mainly related to parameters on relative time in one walking cycle, such as timing of maximum knee extension. These results suggest that parameters related to stride length may strongly characterize the gait of older adults. In other words, the gait of older adults may be recognized mainly from their short stride length. The low explanation of variance for timing parameters may suggest that the pattern of kinematic change in one gait cycle is determined strictly, whereas kinematic magnitude is strongly affected by aging.
