Variability of step kinematics in young and older adults.

Fall-related injuries are the most common and serious medical problems facing older adults. Recent studies of older adults have focused on the variability of step kinematics and the relationship to falling. The accuracy of step variability estimates is proportional to the number of steps that are collected. The use of an instrumented treadmill allows simultaneous collection of spatial and temporal step kinematics for a large number of continuous steps. The current study was conducted to determine the influence of age, walking velocity and handrail use on the variability of step kinematics using a treadmill protocol. Eighteen young adults (average age: 27.7 +/- 3.3 years) and 12 healthy older adults (average age: 73.4 +/- 2.3 years) were recruited from the community. Temporal and spatial gait parameters were quantified using custom designed software from measurements collected during treadmill walking. The primary independent variables were the variability of step length, step width, and step time. Step width variability of older adults was significantly larger than that of young adults. Walking velocity did not influence step kinematic variability. Handrail usage influenced the variability of step length and step width, but not of step time. The present results, and those of previous studies, point to a consistent relationship between age and step width variability. Since step width variability has been implicated in falls, further research is warranted.