Minimum Slip Perturbation Amplitudes Required to Identify Altered Kinematics and Muscle Excitations

Area of Science:

• Biomechanics
• Neuroscience
• Wearable Technology

Background:

• Monitoring gait instability is crucial for identifying individuals at risk of falls.
• Surface electromyography (sEMG) and inertial measurement units (IMUs) are potential tools for detecting subtle changes in gait.
• Understanding the relationship between sensory perception and physiological responses to perturbations is key.

Purpose of the Study:

• To determine the minimum slip perturbation amplitudes detectable by sEMG and IMUs compared to conscious perception thresholds.
• To test the hypothesis that conscious perception thresholds are similar to those detected by sEMG and IMUs.
• To evaluate the potential of using these technologies for screening individuals with sensory or motor deficits.

Main Methods:

• Fifteen healthy young adults underwent controlled slip perturbations during walking.
• Participants reported conscious perception of each slip.
• sEMG and IMU data were analyzed to determine minimal detectable perturbation amplitudes based on signal changes exceeding 3 standard deviations from normal walking.

Main Results:

• The average conscious perception threshold was 0.061 m/s (Δ velocity).
• sEMG detected perturbations at 0.053 m/s (tibialis anterior) and 0.018 m/s (gastrocnemius).
• IMUs detected perturbations at ≤0.016 m/s across most placements, indicating high sensitivity.

Conclusions:

• Minimal detectable amplitudes for muscle reflexes and IMUs are lower than for conscious perception.
• This difference supports using sEMG and IMUs for objective instability monitoring and screening for pathologies.
• IMUs show significant promise for real-world monitoring of gait instability and fall risk.