Modelling the triceps surae muscle-tendon complex for the estimation of length changes during walking.

Area of Science:

• Biomechanics
• Human locomotion
• Musculoskeletal modeling

Background:

• Accurate modeling of the triceps surae muscle-tendon complex is essential for understanding locomotion.
• Previous models often simplify foot mechanics, assuming rigidity and pure sagittal motion.

Purpose of the Study:

• To evaluate the validity of assuming foot rigidity and pure sagittal motion in triceps surae models.
• To quantify the impact of forefoot-rear foot movement on muscle length and velocity estimations.

Main Methods:

• Developed a 3D model of the triceps surae muscle-tendon complex incorporating forefoot-rear foot articulation.
• Collected gait data from six healthy subjects using 3D motion analysis.
• Compared model outputs with and without considering foot articulation, and with pure sagittal motion projections.

Main Results:

• Significant differences in soleus muscle length (late stance/swing) and velocity (early stance) were observed when accounting for foot articulation.
• Foot articulation resulted in a changeable angle (11.8° ± 4.7° SE) during gait.
• Pure sagittal projection analysis showed minimal differences, mainly a constant offset.

Conclusions:

• The assumption of foot rigidity is not fully acceptable for accurate triceps surae muscle-tendon complex modeling during locomotion.
• While sagittal motion is a reasonable approximation, forefoot-rear foot articulation influences key muscle dynamics.
• Clinical applications require careful consideration of potential foot deformities and motion deviations.