The neuromuscular demands of toe walking: a forward dynamics simulation analysis

Area of Science:

• Biomechanics
• Human Movement Science
• Musculoskeletal Modeling

Background:

• Toe walking is a gait deviation characterized by increased ankle plantar flexor muscle activity.
• Understanding the underlying mechanics is crucial for effective clinical interventions.

Purpose of the Study:

• To investigate the relationship between increased muscle activity and decreased ankle joint moment in toe walking using musculoskeletal modeling.
• To analyze the force-generating capacity of ankle plantar flexors during toe versus heel-toe walking.

Main Methods:

• Utilized a detailed musculoskeletal model and forward dynamical simulations to emulate toe and heel-toe walking.
• Assessed plantar flexor force generating capacity by examining muscle contractile states (fiber length, velocity, activation).

Main Results:

• Despite increased soleus (122%) and gastrocnemius (76%) activity, peak ankle moment in late stance decreased during toe walking.
• This decrease was attributed to non-optimal plantar flexor contractile conditions, primarily the force-length relationship.
• Greater muscle activity is required to produce equivalent force, and sustained force generation increases neuromuscular demand.

Conclusions:

• Toe walking, while potentially involving lower peak forces, imposes a higher overall neuromuscular demand on plantar flexors.
• Clinical decisions regarding equinus correction should consider the impact on both ankle moment and plantar flexor force-generating capacity.