Muscle Mechanical Work Adaptations With Increasing Walking Speed

Recent modeling studies of walking at self-selected speeds have identified how individual muscles work in synergy to satisfy the task demands including body support, forward propulsion and swing initiation (e.g. [1, 6]). These analyses revealed that young adults walking at a self-selected speed utilize a distribution of hip and knee extensor muscle force in early stance and ankle plantar flexor and rectus femoris force in late stance to provide support and forward propulsion [6]. However, how these muscles’ putative contributions to these functional tasks change with walking speed is not well understood. Intuitively, increasing walking speed would necessitate an increase in activity for muscles that contribute to forward propulsion. However, increasing walking speed is also associated with longer stride lengths (e.g., [2]), which may require increased activity from those muscles contributing to swing initiation, and increased activity from those muscles contributing to vertical support because the vertical excursion of the body’s center of mass increases.