Biomechanics of forward momentum arrest when walking: Age and gender differences.

Abstract

Abilities to arrest forward momentum suddenly when walking have significant implications in explaining falls and pedestrian related injuries. Experiments were specially designed to investigate age and gender effects on arrest forward momentum by turning and stopping suddenly. Healthy older adults were found to need longer available response time than healthy young adults in both tasks. Older females need longer available response time than older males. To turn suddenly, young females were found to need longer available response time than young males. The age and gender differences were examined through study of the kinematics of the whole body center of mass (CM). The longer time delays of older than young before braking contributed to most of the age differences. The weaker deceleration of females compared to males explains most of the gender differences, especially the gender differences among old. To further relate the CM kinematics to muscle strength and neurological reaction time, two multi-segment direct-dynamics, goal-driven models were constructed. By varying the joint strength, including rates of joint torque development and maximum torques, and neurological reaction time, the age differences appeared to arise from both the longer neurological reaction delays and the slower rates of joint torque development of old. Weaker joint strengths, especially of the ankle plantarflexors, were responsible for most of the gender differences among old. For the gender differences, both maximum joint torque and rate of torque development were found of importance. The effects of gait phase, number of steps used in momentum arrest and differences between stopping and turning were also examined. Age effects in increasing lateral momentum during turning were studied as well. It was concluded that the age declines in arresting forward momentum suddenly when walking are more pronounced among females than males. Three topics for future research were suggested.