Physical Activity, Exercise Physiology, Movement
Muscle Activations and Control of Speed during Normal and Perturbed Walking
(School of Public Health (UMD) Kinesiology Doctoral Student)
Ehtemam, Farzad (UMD), Kiemel, Farzad (UMD), Ehtemam, Farzad
It has been shown that changes in speed is an indicator of health decline in neurological and geriatric populations (1,2). In order to understand the underlying mechanisms of speed control and their variations across different populations, it is necessary to understand how changes in speed affect modulation of muscle activation profiles over time. A steady-state change in muscle activity is the steady-state difference in the activity for two different constant speeds while a transient change in activity is a change due to a brief perturbation that leads to a transient change in speed. Although the steady-state changes have been explored in several studies before (3,4,5), it is not yet understood how the transient changes are related to those observed in steady-state conditions. The purpose of this study was to compare and contrast the transient changes in muscle activations as a function of speed to responses from steady-state conditions. Electromyography (EMG) was recorded from four leg muscles to derive muscle activation profiles and kinematic data was collected to identify gait cycles. To construct transient changes in muscle activations, we used harmonic transfer functions (6,7) to calculate the relationship between perturbations and EMG signals. The result of this study found similarities shared between steady-state and transient changes in muscle activations as the speed of walking changes. Another finding was a decrease in the transient activity with increase in speed prior to heel strike for dorsiflexors and push-off for plantarflexors. This pattern of activity has not been observed before in steady-state conditions and is unique to control of speed during transient responses. To further investigate this new finding, future studies have to compare features of transient responses observed in healthy adults to pathological gait patterns. Supporting figures: References: