Identification of heel strike under a slippery condition
1Chang WR Falls Prevention, LLC, Arlington, VA 22209, USA.
Applied Ergonomics
|September 30, 2017
Summary
Identifying the heel strike instant (HSI) is crucial for quantifying slip severity. Current kinematic methods are unreliable under slippery conditions, necessitating improved HSI identification techniques for accurate slip analysis.
Area of Science:
- Biomechanics
- Human movement analysis
- Injury prevention
Background:
- Kinematics at heel strike instant (HSI) is a common metric for quantifying slip severity.
- Existing methods for HSI identification lack clarity and have not been validated under slippery conditions.
Purpose of the Study:
- To compare different methods of identifying the heel strike instant (HSI) under slippery conditions.
- To evaluate the accuracy of kinematic and force plate-based HSI identification.
Main Methods:
- A glass force plate was used to record the shoe-floor interface during slips.
- Heel strike instants (HSIs) were identified using video analysis, force plate data, and kinematics.
- Comparison of HSIs identified by video, normal force threshold (NFT), and kinematics.
Main Results:
- Video-identified HSIs were more consistent with normal force threshold (NFT) identified HSIs (9.0 ms ± 5.5 ms) compared to kinematics.
- Slips with greater distance between NFT and video HSI showed higher heel horizontal velocity (>0.8 m/s) and lower foot angular velocity (<100 deg/s) at NFT.
- These slips were still in the forward swing phase, indicating potential issues with NFT identification.
Conclusions:
- Current methods, including normal force threshold (NFT), for identifying heel strike instant (HSI) require improvement for accurate slip analysis, particularly under slippery conditions.
- Enhanced HSI identification is crucial for reliable quantification of slip severity and understanding slip dynamics.
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