Walking symmetry is speed and index dependent

Area of Science:

• Biomechanics and Motor Control
• Gait Analysis
• Rehabilitation Science

Background:

• Gait symmetry is a key indicator of gait quality, with various indices proposed for quantification.
• Existing indices include Symmetry Angle (SA), Symmetry Index of the body center of mass (SI_BCoM), and improved Harmonic Ratio (iHR) from lower trunk accelerometry.
• The interrelationships between these indices and the influence of walking speed remain underexplored.

Purpose of the Study:

• To compare gait symmetry indices: SA, SI_BCoM, and iHR.
• To investigate the effect of walking speed on these selected gait symmetry indices.
• To assess the ability of these indices to detect gait asymmetry.

Main Methods:

• Ten healthy adults performed treadmill walking at seven speeds (0.28-1.95 m/s) and simulated asymmetry (ASYM) at 0.83 m/s.
• Marker-based motion capture recorded 3D body center of mass trajectories.
• Lower trunk 3D accelerations were collected using a triaxial accelerometer; SI_BCoM, iHR, and SA were computed.

Main Results:

• No index demonstrated perfect symmetry across all axes and conditions.
• Significant differences were found between SI_BCoM and iHR across all anatomical directions (p < 0.0001).
• Walking speed significantly impacted SI_BCoM and iHR (anteroposterior, craniocaudal), but not SA (p = 0.28). All indices distinguished ASYM from normal gait (p < 0.05).

Conclusions:

• Gait symmetry measurements vary based on the data source, mathematical method, and walking speed.
• Healthy individuals exhibit inherent gait asymmetry, a factor critical for setting rehabilitation goals.
• Clinical gait quality assessments must account for these index-specific and speed-dependent variations.