Muscle force responses during initial-contact gait perturbations and recovery steps

Area of Science:

• Biomechanics
• Human Movement Science
• Motor Control

Background:

• Maintaining dynamic stability during gait is crucial for fall prevention.
• Muscle activation patterns during gait perturbations, particularly at initial contact (IC), are not fully understood.

Purpose of the Study:

• To investigate how individual lower-limb muscle forces change during gait perturbations at IC and in the subsequent recovery step.

Main Methods:

• Healthy women walked on a treadmill with induced perturbations at IC.
• Motion capture and ground reaction forces were used to estimate muscle forces via static optimization in OpenSim.
• Peak muscle forces (PMF) were compared between perturbed/recovery steps and normal gait, with FDR correction.

Main Results:

• During the perturbed step, 5 of 30 muscles showed significant PMF increases after FDR correction, including proximal and biarticular muscles (e.g., biceps femoris, gastrocnemius).
• This indicates a multi-joint stabilization strategy involving key muscles across hip, knee, and ankle.
• While some muscles showed increased PMF during the recovery step, these changes were not statistically significant after FDR correction.

Conclusions:

• Gait perturbations at IC engage a specific set of stabilizing muscles across multiple joints.
• Adaptations in the recovery step require further investigation due to lack of statistical significance.
• Findings offer insights into muscle-level balance recovery mechanisms and inform fall prevention rehabilitation.