Weight-bearing symmetry changes after asymmetric surface stiffness walking

Area of Science:

• Biomechanics
• Neuromotor control
• Gait analysis

Background:

• Gait asymmetry is common in locomotion impairments.
• Split belt treadmill training improves spatial asymmetry but not weight-bearing or propulsion asymmetry.
• Asymmetric surface stiffness walking offers a novel approach to address these persistent gait deficits.

Purpose of the Study:

• To investigate neuromotor adaptations in weight bearing and propulsion asymmetries using asymmetric surface stiffness walking.
• To test the hypothesis that asymmetric stiffness walking elicits aftereffects in weight bearing, propulsion, and plantar flexor activity.

Main Methods:

• Twelve healthy adults walked on an adjustable stiffness treadmill for 10 minutes under asymmetric stiffness conditions.
• Ground reaction forces (GRF) and spatio-temporal measures were recorded using a dual-belt instrumented treadmill before and after the perturbation.
• Plantar flexor muscle activity (gastrocnemius and soleus) was also measured.

Main Results:

• Asymmetric stiffness walking induced a 2.8% asymmetry in vertical GRF at push-off.
• Plantar flexor activity increased on the perturbed side (GAS: 20.7%, SOL: 9.5%).
• Mid-stance vertical GRF decreased (2.2%) and peak braking GRF increased (6.8%) on the perturbed side; propulsion GRF did not increase as hypothesized.

Conclusions:

• Asymmetric stiffness walking promotes neuromotor adaptation, leading to a relative increase in push-off in the targeted limb, primarily in the vertical component.
• Further research is warranted to explore gait adaptation to asymmetric stiffness walking in individuals with existing push-off asymmetries.