Experimental evidence supporting isometric functioning of the extrinsic toe flexors during gait

Area of Science:

• Biomechanics
• Human Locomotion
• Musculoskeletal System

Background:

• Extrinsic toe flexors, flexor hallucis longus (FHL) and flexor digitorum longus (FDL), are crucial for stabilizing the longitudinal arch and managing forefoot loads during gait.
• A hypothesis suggests these muscles function isometrically during stance for efficient energy transfer, but in vivo evidence is limited.

Purpose of the Study:

• To experimentally investigate the in vivo function of extrinsic toe flexors during the stance phase of gait.
• To determine if FHL and FDL muscles operate isometrically or with significant excursion during gait stance.

Main Methods:

• Eight lower extremity cadavers were subjected to a robotic simulation of gait stance.
• Tendon excursions and forces of FHL and FDL were measured under force feedback and isometric displacement control strategies.
• Plantar pressure distributions were also recorded during the simulated stance phase.

Main Results:

• Tendon excursions for FHL (7.18 mm) and FDL (6.32 mm) were minimal relative to optimal muscle fiber length (13.6% and 14.2%).
• No significant differences in instantaneous tendon forces or plantar pressure variables were observed between the two control strategies (P=0.112-0.912).

Conclusions:

• The findings support the hypothesis that extrinsic toe flexors function isometrically during the stance phase of gait.
• Isometric function of FHL and FDL contributes to efficient biomechanical energy transfer during locomotion.