Local dynamic stability of treadmill walking: intrasession and week-to-week repeatability

Area of Science:

• Biomechanics
• Gait Analysis
• Neurology

Background:

• Repetitive falls significantly impact the quality of life for the elderly and individuals with neurological disorders.
• Early indicators of impaired dynamic balance are crucial for fall prevention during walking.
• Local dynamic stability (LDS), assessed by divergence exponents, is a potential fall risk index, but its reliability requires further investigation.

Purpose of the Study:

• To explore the intrasession and intersession repeatability of gait local dynamic stability (LDS) measurements.
• To evaluate LDS as a reliable index for assessing fall risk in healthy individuals.

Main Methods:

• Ninety-five healthy participants underwent 5-minute treadmill walking sessions.
• Trunk acceleration was recorded using a 3D accelerometer.
• LDS was estimated using three time scales (λ4-10, λ1, λ0.5) to assess gait stability.

Main Results:

• Intrasession repeatability showed moderate to high Intraclass Correlation Coefficients (ICCs), particularly for λ1 and λ0.5.
• Intersession ICCs were around 0.60, indicating lower repeatability across different days.
• The medio-lateral λ0.5 measurement demonstrated the best reliability, capable of detecting moderate individual changes (20%).

Conclusions:

• Gait LDS shows good intrasession reliability, but lower intersession reliability limits its use for single-day assessments.
• The medio-lateral λ0.5 is the most reliable LDS measure for detecting gait balance changes.
• Averaging multiple LDS measurements taken on different days is recommended for a more accurate assessment of true gait stability and fall risk.